Distributed antenna system network time delay measurement and compensation method and system

Abstract

The invention provides a distributed antenna system network time delay measurement and compensation method and system, and relates to the technical field of wireless communication. The measurement method comprises the following steps: acquiring a CPRI standard time delay parameter of each device in a DAS network; the CPRI standard time delay parameters comprise downlink one-way time delay, uplink one-way time delay, loopback total time delay, internal path time delay, fixed time delay, uplink buffer time delay and downlink buffer time delay; the internal path time delay comprises a first path time delay and a second path time delay; based on the CPRI standard time delay parameter, total time delay of each end-to-end communication link in the DAS network is calculated, and the total time delay comprises downlink total time delay and uplink total time delay; and each communication link comprises at least one section of optical fiber chain. According to the invention, the scheme of multilink refined delay measurement and adaptive dynamic compensation in the DAS network is realized.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, specifically to synchronization optimization technology for distributed antenna systems (DAS), and more particularly to a method and system for measuring and compensating network delay of distributed antenna systems based on the Common Public Radio Interface (CPRI) protocol. Background Technology

[0002] A Distributed Antenna System (DAS) effectively extends the coverage of wireless signals through a cascaded architecture of main units, hub units, and remote units. In actual deployment, each remote unit is connected to the main unit via fiber optic links of varying lengths, forming multiple end-to-end communication links. Since the transmission rate of optical signals in optical fibers is constant (approximately 2 × 10⁻⁶), this system leverages the existing fiber optic connections. 8 The difference in physical link length (m / s) directly leads to different signal transmission delays. For example, 5km of optical fiber produces a delay of about 25μs, while 10km of optical fiber produces a delay of about 50μs.

[0003] This inconsistency in uplink and downlink latency between communication links can cause serious network problems: downlink (DL) signals arrive at the air interfaces of different RUs at different times, leading to chaotic terminal handover; uplink (UL) signals return to the master unit from different remote units at different times, causing receivers to lose synchronization. These problems ultimately manifest as a decrease in handover success rate, a reduction in data throughput, and a deterioration in communication quality.

[0004] To address the aforementioned latency issues, most methods measure overall latency based on a single CPRI link. However, this approach cannot effectively decompose and measure the latency contribution of each sub-link (fiber segment) in a multi-level cascaded DAS scenario. Furthermore, if latency compensation is mostly statically configured, it cannot dynamically adapt to changes in network topology or device status. Therefore, there is an urgent need for a solution that can achieve refined latency measurement and adaptive dynamic compensation across multiple links within a DAS network. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for measuring and compensating network delay in a distributed antenna system, thereby improving the aforementioned problems. To achieve this objective, the technical solution adopted by this invention is as follows: In a first aspect, the present invention provides a method for measuring network delay in a distributed antenna system, comprising: Obtain the CPRI standard delay parameters for each unit in the DAS network; the CPRI standard delay parameters include: downlink one-way delay, uplink one-way delay, total loopback delay, and internal path delay, wherein the internal path delay includes first path delay, second path delay, fixed delay, uplink buffer delay, and downlink buffer delay; CPRI represents Common Public Radio Interface; DAS represents Distributed Antenna System; Based on the CPRI standard delay parameters, the total delay of each end-to-end communication link in the DAS network is calculated, including the total downlink delay and the total uplink delay; wherein each communication link contains at least one fiber optic link; CPRI represents Common Radio Interface; DAS represents Distributed Antenna System.

[0006] Finally, based on the decomposed sub-link delays and the path delays and fixed delays within each unit, the actual total downlink delay and total uplink delay of each end-to-end communication link are accurately calculated.

[0007] Furthermore, the CPRI standard delay parameters are sent to the master unit in the DAS network.

[0008] Furthermore, for any communication link, the expression for calculating the total downlink delay of the communication link is as follows: ; Wherein, ΣT12 is the sum of the downlink one-way delays of all optical fiber links in the downlink direction of the communication link, T2a is the first path delay of the remote unit in the communication link, and ΣTBDelayDL is the sum of the downlink buffer delays of all optical fiber links in the downlink direction of the communication link. The expression for calculating its total uplink delay is as follows: ; Wherein, ΣT34 is the sum of the uplink one-way delays of all optical fiber links in the uplink direction of the communication link, Ta3 is the second path delay of the remote unit in the communication link, and ΣTBdelayUL is the sum of the uplink buffer delays of all optical fiber links in the uplink direction of the communication link.

[0009] Furthermore, obtaining the downlink one-way delay and uplink one-way delay of the optical fiber link includes: Based on the total loopback delay of the CPRI protocol, obtain the time difference between the control word transmission timestamp and the reception timestamp; Based on the time difference and the internal fixed delay of the remote unit, the downlink one-way delay and uplink one-way delay of the optical fiber link are calculated. The calculation formulas for the downlink one-way delay and the uplink one-way delay are shown below; ; in, Internal fixed delay; Based on the symmetrical characteristics of the uplink and downlink communication links, the values ​​of the downlink one-way delay and the uplink one-way delay are equal.

[0010] Second aspect This invention also provides a method for network delay compensation in a distributed antenna system, comprising: The total latency of all communication links is obtained based on the aforementioned measurement method; The communication link with the largest total latency is selected as the latency reference in both the uplink and downlink directions; Calculate the time delay difference between each link and the corresponding directional reference as the compensation value; send the compensation value to the remote unit of the corresponding link; The remote unit delays the transmission of downlink and uplink signals according to the compensation value, so as to achieve air interface delay alignment of downlink signals and synchronous arrival of uplink signals at the main unit.

[0011] The present invention requires the remote unit to perform programmable delay operations on both downlink and uplink signals at the physical layer: delaying the transmission of downlink signals to achieve air interface alignment, and delaying the transmission of uplink signals to achieve master unit reception synchronization.

[0012] Furthermore, the remote unit includes a programmable digital delay unit.

[0013] Furthermore, the compensation method also includes dynamically updating the delay difference: Based on a preset period or when a change in the state of a communication link in the DAS network is detected, the measurement method is re-executed to obtain the updated total latency of each communication link, and the latency difference is recalculated and sent based on the updated total latency. The changes in the communication link status include: hub unit or remote unit restart, fiber optic link length adjustment, and CPRI link reconnection.

[0014] Third aspect This invention also provides a distributed antenna system network delay compensation system for implementing the above method, comprising: a main unit, at least one hub unit, and at least one remote unit. The remote unit and hub unit are configured to acquire and report their own CPRI standard delay parameters. The main unit is configured to: receive and aggregate all reported delay parameters; calculate the total uplink and downlink delays of each communication link; select a reference and calculate the delay difference; and send the delay difference to the corresponding RU. The remote unit is further configured to delay the transmission of signals based on the received delay difference.

[0015] Furthermore, the main unit is also configured to periodically and / or re-trigger the process of acquiring, calculating, and sending delay parameters when a change in the communication link status is detected; the change in the communication link status includes: hub unit or remote unit restart, fiber optic link length adjustment, and CPRI link reconnection.

[0016] The beneficial effects of this invention are as follows: This invention fully utilizes the standard delay parameters defined by the CPRI protocol to achieve nanosecond-level fine-grained delay decomposition and measurement for each communication link and even each fiber optic link. This invention, by periodically detecting parameters in the entire network system and dynamically updating the latency difference in conjunction with event triggering, can automatically adapt to changes in network status such as fiber optic aging, equipment restart, and link adjustment. This invention uses the communication link with the longest total delay as the reference delay for bidirectional compensation in the uplink and downlink directions, ensuring strict alignment of all downlink signals at the air interface and synchronous arrival of all uplink signals at the master unit. The air interface synchronization error can be controlled within 10ns. This invention is based entirely on the existing architecture and parameter system of the CPRI protocol, without the need for additional GPS or dedicated synchronization hardware, which significantly reduces deployment and maintenance costs.

[0017] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the testing method and compensation method provided in the embodiments of the present invention; Figure 2 This is a schematic diagram illustrating the CPRI latency standard interface parameter definition provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of a multi-link heterogeneous topology of a DAS network provided in an embodiment of the present invention; Figure 4 A schematic diagram of the downlink (DL) delay measurement and compensation process provided in an embodiment of the present invention; Figure 5 A schematic diagram of the uplink (UL) direction delay measurement and compensation process provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] English definition Distributed Antenna System (DAS).

[0023] Common Public Radio Interface (CPRI)

[0024] Example 1: This embodiment provides a method for measuring and compensating network delay in a distributed antenna system.

[0025] See Figure 1 This embodiment provides a method for measuring network delay in a distributed antenna system. The measurement method is centrally controlled and executed by the master unit (MU), and the specific steps are as follows: Step S100: Obtain the CPRI standard delay parameters of each device in the DAS network; the CPRI standard delay parameters include: downlink one-way delay T12, uplink one-way delay T34, total loopback delay T14, internal path delay, fixed delay Toffset, uplink buffer delay TBdelayUL, and downlink buffer delay TBDelayDL; the internal path delay includes the first path delay T2a and the second path delay Ta3; like Figure 2As shown, the CPRI standard delay parameters used in this invention and their mapping in DAS are defined as follows: where REC represents the master unit MU, the first-level RE represents the hub unit HU, and the second-level RE represents the remote unit RU. T12: Downlink one-way delay, which refers to the delay experienced by the signal from port R1 of the main unit MU to port R2 of the remote unit RU, including fiber optic transmission delay and basic equipment processing delay.

[0026] T34: Uplink one-way delay, refers to the delay experienced by the signal from port R3 of the remote unit RU to port R4 of the main unit MU, which also includes fiber optic transmission delay and basic equipment processing delay.

[0027] T14: Total Loopback Delay. This refers to the total time it takes for a control word to travel from port R1 of the master unit (MU), loop back through the remote unit (RU), and return to port R4 of the master unit (MU). In some specific embodiments, T14 is composed of the delays of multiple modules within the FPGA, including timestamp acquisition, forward error correction (FEC) encoding / decoding pipeline delay, receive / transmit FIFO buffer delay, gearbox (used for CPRI frame packing / unpacking) delay, and inherent system delays.

[0028] T2a: First path delay of the remote unit RU. It refers to the delay of the signal from the receiving port R2 of the remote unit RU to its internal core processing module Ra.

[0029] Ta3: Second path delay of the remote unit RU. This refers to the delay in time for a signal to travel from the internal core processing module Ra of the remote unit RU to its transmitting port R3.

[0030] Toffset: Fixed internal latency of the remote unit RU. Specifically refers to the fixed internal time required for the remote unit RU to receive data from port R2 and transmit data from port R3.

[0031] TBdelayUL: Uplink buffer delay, refers to the dynamic delay introduced by the hub unit (HU) during uplink data transmission due to data buffering and processing (such as gearbox, FIFO); TBDelayDL: Downlink buffer delay, refers to the dynamic delay introduced by the hub unit (HU) during downlink data transmission due to data buffering and processing (such as gearbox, FIFO).

[0032] Inherent system latency: refers to non-configurable baseline latency such as hardware circuit wiring latency and fixed protocol stack processing time.

[0033] See Figure 3The DAS network comprises a master unit MU, first hub units HU0 and HU1, and first remote units RU0, second remote units RU1, and third remote units RU2, forming four end-to-end communication links Link0-Link3, each with varying lengths. The master unit MU sends latency parameter acquisition commands to the first hub unit HU0, the second hub unit HU1, and the three remote units RU0, RU1, and RU2. Upon receiving the commands, each unit independently acquires and calculates its own relevant latency parameters through its internal FPGA and software logic.

[0034] For example, the first hub unit HU0 will measure T12 (or T34) of the fiber optic link between itself and the main unit MU, as well as its own TBDelayDL (or TBdelayUL); the second remote unit RU1 will measure its T2a, Ta3, Toffset, and T12 / T34 of the link with the first hub unit HU0, etc.

[0035] Step S200: Based on the CPRI standard delay parameters, calculate the total delay of each end-to-end communication link in the DAS network; after receiving all CPRI standard delay parameters, the main unit MU performs centralized processing and calculation.

[0036] For a cascaded link containing multiple fiber segments, such as Figure 3 The communication link Link2 shown is: main unit MU - first hub unit HU0 - second remote unit RU1. The main unit MU first obtains the total loopback delay T14 of the entire link. Based on the symmetrical characteristics of the CPRI fiber optic link's transmit and receive paths, i.e., the downlink one-way delay T12 is equal to the uplink one-way delay T34, combined with the fixed delay Toffset reported by the first remote unit RU1, the downlink one-way delay T12 and the uplink one-way delay T34 can be obtained. The specific steps for obtaining the downlink one-way delay and uplink one-way delay of the fiber optic link include: First, for a DAS network containing multiple links, the total loopback delay T14 based on the CPRI protocol is used to obtain the time difference between the control word transmission timestamp and the reception timestamp; the formula for calculating the total loopback delay T14 is as follows: ; Based on the symmetrical characteristics of the uplink and downlink communication links, the values ​​of the downlink one-way delay and the uplink one-way delay are equal. Let T12_S1 = T34_S1 and T12_S2 = T34_S2. T12_S1 is the downlink one-way delay of the first communication link Link1, and T34_S1 is the uplink one-way delay of the first communication link Link1. T12_S2 is the downlink one-way delay of the second communication link Link2, and T34_S2 is the uplink one-way delay of the second communication link Link2.

[0037] Calculate the downlink one-way delay T12 and the uplink one-way delay T34 of the optical fiber link; The calculation formulas for the downlink one-way delay and the uplink one-way delay are shown below; ; in, With a fixed delay, the downlink one-way delay T12 and uplink one-way delay T34 of each sub-link segment can be uniquely calculated.

[0038] The total delay is obtained based on the downlink one-way delay T12, the uplink one-way delay T34, the internal path delay of the remote unit, and the buffer delay of each unit. The calculation formula is as follows: Total downlink latency: ; Total uplink latency: ; Wherein, ΣT12 is the sum of the downlink one-way delays of all optical fiber links in the downlink direction of the communication link Link, T2a is the first path delay of the remote unit RU in the communication link Link, ΣTBDelayDL is the sum of the downlink buffer delays of all optical fiber links in the downlink direction of the communication link Link; ΣT34 is the sum of the uplink one-way delays of all optical fiber links in the uplink direction of the communication link Link, Ta3 is the second path delay of the remote unit RU in the communication link Link, and ΣTBdelayUL is the sum of the uplink buffer delays of all optical fiber links in the uplink direction of the communication link Link.

[0039] This embodiment provides a network delay compensation method for a distributed antenna system. The method mainly involves obtaining the total delay using the above measurement method and then performing a compensation phase on the uplink total delay and downlink total delay in the main unit. The compensation process is as follows Figure 4 Downward and Figure 5 As shown in the top row.

[0040] Step S300: Select the communication link with the largest total delay as the delay reference for the corresponding direction in both the uplink and downlink directions; The main unit (MU) summarizes and calculates the total delay values ​​of all communication links in the downlink and uplink directions, and selects the communication link with the largest total delay value as the "delay reference" for that direction.

[0041] Step S400: Obtain the delay difference between each communication link and the delay reference in the corresponding direction, wherein the delay difference is the compensation value in the corresponding direction; Downward compensation value: ; Upward compensation value: ; in, As the time delay reference in the downlink direction, This represents the total downlink latency of the current communication link. As the time delay reference for the uplink direction, This represents the total uplink latency of the current communication link.

[0042] Step S500: Send the delay difference corresponding to each communication link Link to the remote unit RU of that communication link Link; The master unit MU sends the calculated downlink compensation value TcompDL and uplink compensation value TcompUL to the remote unit RU of the corresponding communication link Link.

[0043] Step S600: Each remote unit RU delays the transmission of downlink and uplink signals according to the received delay difference, so as to achieve downlink signal air interface delay alignment and uplink signal synchronous arrival at the main unit MU. Upon receiving the compensation value, the remote unit RU immediately adjusts its internal delay compensation module. Specifically, the remote unit RU has a programmable digital delay unit (such as a configurable depth FIFO or digital delay line). The remote unit RU converts the received time-in-time compensation value into the required number of clock cycles based on the local system clock frequency, and configures the delay unit accordingly.

[0044] For downlink signals: After receiving the downlink direction compensation value from the master unit MU, the remote unit RU makes it flow through the delay unit, is buffered for a specified time, and then transmits it to the air interface, so that it and the downlink signal of the delay reference arrive at the master unit MU in their respective coverage areas at the same time.

[0045] For uplink signals: After receiving and processing the uplink signal from the master unit MU, the remote unit RU makes the uplink direction compensation value flow through the delay unit before sending it to the master unit MU. The value is buffered for a specified time before being sent, thereby ensuring that the uplink signals of all communication links can arrive at the MU synchronously for processing.

[0046] Step S800: Periodically and / or when a change in the state of a communication link in the DAS network is detected, the measurement method is re-executed to obtain the updated total delay of each communication link, and the delay difference is recalculated and sent based on the updated total delay; The main unit (MU) automatically initiates a new round of delay measurement and compensation at a certain period, which is 9 seconds in this embodiment, to update all CPRI standard delay parameters and compensation values.

[0047] In some embodiments, when the master unit MU detects a change in network status through the network management interface or CPRI link status word (such as HU / RU device restart, physical adjustment of fiber optic link length, CPRI link disconnection and reconnection, etc.), it immediately triggers a network-wide latency measurement and latency compensation to quickly adapt to network changes.

[0048] Example 2: This embodiment provides a distributed antenna system network delay compensation system, including a main unit MU, several hub units HU, and remote units RU. The system achieves the aforementioned function through the coordinated configuration of each unit.

[0049] Both the remote unit RU and the hub unit HU include a parameter acquisition module and a reporting interface. The parameter acquisition module is typically implemented using FPGA logic and is responsible for real-time measurement and calculation of various CPRI standard delay parameters of this unit. The CPRI standard delay parameters include: downlink one-way delay, uplink one-way delay, total loopback delay, internal path delay, fixed delay, uplink buffer delay, and downlink buffer delay. The reporting interface is responsible for packaging parameters into a CPRI protocol message and sending it to the master unit (MU). The remote RU additionally includes a programmable delay unit, used to delay the transmission of downlink and uplink signals according to the received delay difference.

[0050] The main unit (MU) includes a parameter processing module, a calculation module, and a scheduling module. The parameter processing module receives and summarizes the CPRI standard delay parameters reported by all remote units (RU) and hub units (HU); Based on the CPRI standard delay parameters, the calculation module calculates the total downlink delay and total uplink delay of each end-to-end communication link in the DAS network; and selects the communication link with the largest total delay in the uplink and downlink directions as the delay reference for the corresponding direction, and calculates the delay difference of each other communication link relative to the delay reference. The scheduling module sends the calculated delay difference of each communication link to the corresponding remote unit; and is responsible for periodically or in response to events to initiate measurement commands and send compensation control commands to each remote unit (RU).

[0051] By implementing the above methods and systems, this invention can achieve high-precision, adaptive latency synchronization of multiple links in DAS networks without the need for additional hardware, thus significantly improving network performance.

[0052] It should be noted that the specific manner in which each module performs its operation in the apparatus described in the above embodiments has been described in detail in the embodiments of the method, and will not be elaborated here.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0054] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for measuring network delay in a distributed antenna system, characterized in that, include: Obtain the CPRI standard latency parameters for each device in the DAS network; The CPRI standard latency parameters include: downlink one-way latency, uplink one-way latency, total loopback latency, internal path latency, fixed latency, uplink buffer latency, and downlink buffer latency; the internal path latency includes first path latency and second path latency. Based on the CPRI standard delay parameters, the total delay of each end-to-end communication link in the DAS network is calculated, including the total downlink delay and the total uplink delay; each communication link contains at least one fiber optic link.

2. The method for measuring network delay in a distributed antenna system according to claim 1, characterized in that, The CPRI standard delay parameters are sent to the master unit in the DAS network.

3. The method for measuring network delay in a distributed antenna system according to claim 2, characterized in that, For any communication link, the expression for calculating the total downlink delay of the communication link is as follows: ； Wherein, ΣT12 is the sum of the downlink one-way delays of all optical fiber links in the downlink direction of the communication link, T2a is the first path delay of the remote unit in the communication link, and ΣTBDelayDL is the sum of the downlink buffer delays of all optical fiber links in the downlink direction of the communication link. The expression for calculating its total uplink delay is as follows: ； Wherein, ΣT34 is the sum of the uplink one-way delays of all optical fiber links in the uplink direction of the communication link, Ta3 is the second path delay of the remote unit in the communication link, and ΣTBdelayUL is the sum of the uplink buffer delays of all optical fiber links in the uplink direction of the communication link.

4. The method for measuring network delay in a distributed antenna system according to claim 3, characterized in that, Obtaining the downlink one-way delay and uplink one-way delay of the optical fiber link includes: Based on the total loopback delay of the CPRI protocol, obtain the time difference between the control word transmission timestamp and the reception timestamp; Based on the time difference and the internal fixed delay of the remote unit, the downlink one-way delay and uplink one-way delay of the optical fiber link are calculated. The calculation formulas for the downlink one-way delay and the uplink one-way delay are shown below; ； in, Internal fixed delay; Based on the symmetrical characteristics of the uplink and downlink communication links, the values ​​of the downlink one-way delay and the uplink one-way delay are equal.

5. A method for network delay compensation in a distributed antenna system, characterized in that, Based on the measurement method described in any one of claims 1 to 4, the total uplink delay and total downlink delay of all communication links in the DAS network are obtained; In both the uplink and downlink directions, the communication link with the largest total latency is selected as the latency reference for the corresponding direction. Obtain the delay difference between each communication link and the delay reference in the corresponding direction, where the delay difference is the compensation value in the corresponding direction; The delay difference corresponding to each communication link is sent to the remote unit of that communication link; The remote unit delays the transmission of downlink and uplink signals according to the received delay difference.

6. The distributed antenna system network delay compensation method according to claim 5, characterized in that, The remote unit includes a programmable digital delay unit.

7. A method for network delay compensation in a distributed antenna system according to claim 5 or 6, characterized in that, It also includes dynamically updating the latency difference: Based on a preset period or when a change in the state of a communication link in the DAS network is detected, the measurement method is re-executed to obtain the updated total latency of each communication link, and the latency difference is recalculated and sent based on the updated total latency. The changes in the communication link status include: hub unit or remote unit restart, fiber optic link length adjustment, and CPRI link reconnection.

8. A method for network delay compensation in a distributed antenna system according to claim 5 or 6, characterized in that, The period is 1 to 10 seconds.

9. A distributed antenna system network delay compensation system, used to implement the method according to any one of claims 1 to 8, characterized in that, The system includes: a main unit, at least one hub unit, and at least one remote unit; The remote unit and hub unit are configured as follows: Acquire and report its own CPRI standard latency parameters; the CPRI standard latency parameters include: downlink one-way latency, uplink one-way latency, total loopback latency, internal path latency, fixed latency, uplink buffer latency, and downlink buffer latency; The main unit is configured as follows: Receive and summarize the CPRI standard delay parameters reported by all remote units and hub units; Based on the CPRI standard delay parameters, the total downlink delay and total uplink delay of each end-to-end communication link in the DAS network are calculated respectively. In both the uplink and downlink directions, the communication link with the largest total delay is selected as the delay reference for the corresponding direction, and the delay difference of each other communication link relative to the delay reference is calculated. The calculated delay difference of each communication link is sent to the corresponding remote unit; The remote unit is further configured to delay the transmission of the downlink signal and the uplink signal respectively based on the received delay difference.

10. A distributed antenna system network delay compensation system according to claim 9, characterized in that, The main unit is also configured to periodically and / or re-trigger the process of acquiring, calculating and sending delay parameters when a change in the communication link status is detected; The changes in the communication link status include: hub unit or remote unit restart, fiber optic link length adjustment, and CPRI link reconnection.

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