MIMO order reduction aided method

Abstract

The application provides a MIMO order reduction auxiliary method, a method for BBU to perform adaptive MIMO order reduction processing in a SU-MIMO scene, and is used for realizing adaptive processing of the BBU on downlink SU-MIMO transmission when a part of antennas of a RRU fails. The application provides sensing of a downlink transmission link by the BBU, so that the BBU can adaptively adjust the number of data streams of downlink SU-MIMO transmission according to air interface channel quality and a downlink transmission channel of the RRU, and finally improves transmission performance of the downlink.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to a MIMO order reduction auxiliary method. BACKGROUND

[0002] MIMO technology can multiply the capacity and spectrum utilization of communication system without increasing bandwidth. It can be defined as the existence of multiple independent channels between the sending end and the receiving end, that is, there is sufficient spacing between the antenna units, thus eliminating the correlation between signals among antennas, improving the link performance of signals and increasing the data throughput. Research shows that in the Rayleigh fading channel environment, OFDM system uses MIMO technology to improve capacity.

[0003] Using MIMO system is an effective method to improve spectrum efficiency. Multipath fading is the main factor affecting communication quality, but MIMO system can effectively use the influence of multipath to improve system capacity. System capacity is limited by interference, and cannot be improved by increasing transmission power. However, MIMO structure can obtain high system capacity without increasing transmission power. In OFDM system, using multiple transmitting antennas is actually applying multiple transmitting antenna technology on each subchannel as needed, and each subchannel corresponds to a multiple antenna subsystem and a multiple transmitting antenna OFDM system.

[0004] MIMO space division multiplexing includes SU-MIMO and MU-MIMO. SU-MIMO means single-user MIMO, and spatially multiplexed data streams are scheduled to a single user to improve the transmission rate and spectrum efficiency of the user; MU-MIMO means multi-user MIMO, and spatially multiplexed data streams are scheduled to multiple users, and multiple users share the same time-frequency resource through space division, which can significantly improve the throughput and capacity of the entire cell. For users with large spatial isolation and low correlation, beam domain pairing can be performed to achieve the gain of multi-user spatial diversity.

[0005] The core of MIMO technology is a multi-antenna transceiver system. Whether it is SU-MIMO or MU-MIMO, to support the transmission of spatial multi-flow data, a plurality of parallel data transmission channels need to be established in space through multiple antennas. The number of spatial parallel data transmission channels in MIMO transmission is related to the channel quality, and the acquisition of the channel quality depends on signal measurement. The main idea is that the transmitting end sends a known sequence of reference signals, and the receiving end solves the channel according to the received sequence. In NR, the downlink channel measurement is generally measured by CSI-RS, and the uplink channel is generally measured by SRS. For downlink transmission, the terminal user measures the CSI-RS and reports the measurement results through CSI. The reported measurement indicators can include rank indication RI, precoding matrix indication PMI, channel quality indication CQI, and CSI-RS resource indication CRI. The rank indication RI indicates the optimal number of spatial transmission layers, the PMI is the precoding matrix suggested by the terminal for the BBU to use, and the BBU schedules the terminal according to the CSI report of the terminal.

[0006] When the channel quality fed back by the terminal meets certain conditions, the BBU will probably select the SU-MIMO mode to transmit downlink data to the terminal, and the number of spatial transmission layers depends on the rank indication RI value reported by the terminal through CSI, as shown in Figure 1 The rank indication RI value fed back by the terminal depends on the algorithm of each terminal manufacturer, and the RI value fed back by each terminal may not be the same for the same channel quality, and even may feed back an incorrect result in some scenarios. For example, when part of the antenna equipment connected to the RRU fails, the number of available downlink transmission antennas decreases, and under normal circumstances, the rank indication RI value reported by the terminal through CSI should be less than the number of downlink antennas that can be used for transmission, but due to the defects in the downlink CSI-RS measurement algorithm of some terminals in this scenario, the reported rank indication RI value may be incorrect, or even greater than the actual number of available downlink antennas. Since the BBU cannot perceive the antenna failure of the RRU, it still sends the CSI-RS reference signal according to the maximum number of antennas supported by the RRU, and determines the actual number of SU-MIMO downlink multi-flow transmission layers according to the rank indication RI value reported by the terminal, thereby causing the number of downlink transmission flows to be unmatched with the actual number of downlink transmission antennas. The failed antenna cannot carry the downlink multi-flow signal scheduled by the BBU, which makes it difficult for the terminal to correctly decode the received data, resulting in low downlink transmission rate, terminal re-establishment, or even disconnection, and the terminal cannot adaptively perform SU-MIMO downlink transmission. SUMMARY

[0007] The present application provides a MIMO order reduction auxiliary method for realizing adaptive processing of BBU to downlink SU-MIMO transmission when RRU partial antenna fails, providing BBU perception to downlink transmission link, so that BBU can adaptively adjust the number of data streams of downlink SU-MIMO transmission according to air interface channel quality and RRU downlink transmission channel, and finally improve the transmission performance of downlink.

[0008] The present application comprises the following steps:

[0009] 1) BBU sends multi-antenna port CSI-RS reference signal through RRU;

[0010] 2) terminal feeds back CSI signal by measuring CSI-RS reference signal, including rank indication RI, recommended precoding matrix PMI and other information

[0011] 3) physical layer receives and analyzes the CSI signal fed back by the terminal and forwards it to the MAC layer;

[0012] 4) MAC scheduler performs SU-MIMO scheduling according to the information reported by the terminal;

[0013] 5) RRU detects downlink transmitting antenna failure, and sends the failed antenna information to OAM through the management surface M;

[0014] 6) OAM synchronizes the failed antenna failure information to the MAC scheduler;

[0015] 7) MAC scheduler perceives the downlink transmitting antenna situation, and when performing downlink SU-MIMO scheduling, comprehensively selects appropriate RI / PMI for the terminal according to the CSI reported by the terminal and the actual available downlink antenna quantity; at the same time, the sending of downlink CSI-RS is also adjusted according to the available downlink antenna, so as to ensure that the number of antenna ports of CSI-RS is not greater than the number of downlink transmitting antennas, and improve the accuracy of reference signal sending.

[0016] Further improvement, assuming that RRU has M antennas for receiving and transmitting data, and the rank indication RI value reported by the terminal is N, the maximum downlink transmission layer selected by BBU when performing downlink SU-MIMO scheduling is min{M, N}.

[0017] Assuming that the RRU fails, X antennas cannot normally transmit and receive data due to the failure, and if the BBU cannot sense the antenna failure, the number of layers of SU-MIMO is selected as min{M, N} when performing downlink scheduling, and part of the downlink data cannot be transmitted on the failed antenna, resulting in possible decoding errors of the terminal, causing low rate. If the RRU synchronizes the antenna failure information to the MAC scheduler through the M surface, the maximum transmission layer number = min{M-X, N} is selected when performing downlink scheduling. Similarly, the BBU MAC also synchronizes the antenna failure information when performing resource allocation of the downlink CSI-RS reference signal, and the maximum antenna port number of the selected CSI-RS = min{M-X, N}, which can also improve the accuracy of the terminal measuring the reference signal.

[0018] The present application has the advantages of:

[0019] 1. The method for BBU to perform adaptive MIMO down-order processing in the SU-MIMO scene, which is used to realize the adaptive processing of the BBU on the downlink SU-MIMO transmission when the RRU part of the antenna fails.

[0020] 2. The present application provides the sensing of the BBU on the downlink transmission link, so that the BBU can adaptively adjust the number of data streams of the downlink SU-MIMO transmission according to the air interface channel quality and the RRU downlink transmission channel, and finally improve the transmission performance of the downlink.

[0021] 3. The comprehensive sensing ability of the BBU scheduler on the data transmission in the SU-MIMO scene can be improved, the processing ability of the downlink data link hardware failure in terms of performance is improved, so that the BBU can select the parameters that are most suitable for the characteristics of the downlink transmission link when performing downlink SU-MIMO scheduling, adaptively adjust the down-order processing of the SU-MIMO, and improve the data decoding success rate of the terminal. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 It is a schematic diagram of SU-MIMO data transmission in the prior art;

[0024] Figure 2 It is a schematic diagram of SU-MIMO data transmission in the present application;

[0025] Figure 3 The flowchart of the detailed description of the present application is shown. Embodiment

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely in the embodiments of the present application with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0027] The SU-MIMO data transmission schematic diagram provided by the embodiments of the present application is shown in Figure 2 The specific implementation flowchart is shown in Figure 3

[0028] The technical solutions of the present application are as follows:

[0029] 1) BBU sends multi-antenna port CSI-RS reference signal through RRU

[0030] 2) The terminal feeds back CSI including rank indication RI, recommended precoding matrix PMI and other information by measuring the CSI-RS

[0031] 3) The physical layer receives and analyzes the CSI fed back by the terminal and forwards it to the MAC layer

[0032] 4) The MAC scheduler performs SU-MIMO scheduling according to the information reported by the terminal

[0033] 5) The RRU detects the failure of the downlink transmitting antenna, and sends the invalid antenna information to the OAM through the management plane M

[0034] 6) The OAM synchronizes the invalid antenna failure information to the MAC scheduler

[0035] 7) The MAC scheduler can perceive the situation of the downlink transmitting antenna, and when performing downlink SU-MIMO scheduling, it can comprehensively select the appropriate RI / PMI pair for the terminal according to the CSI reported by the terminal and the actual available downlink antenna quantity

[0036] 8) The transmission of the downlink CSI-RS is also adjusted according to the available downlink antenna, so as to ensure that the number of antenna ports of the CSI-RS is not greater than the number of downlink transmitting antennas, and to improve the accuracy of the reference signal transmission

[0037] Suppose that the RRU has M antennas for receiving and transmitting data, the rank indication RI value reported by the terminal is N, and the maximum number of downlink transmission layers selected by the BBU when performing downlink SU-MIMO scheduling = min{M, N}.

[0038] ​Suppose that the RRU fails, X antennas cannot normally transmit and receive data due to the failure, and if the BBU cannot sense the antenna failure, the number of layers of SU-MIMO is selected as min{M, N} when performing downlink scheduling, and part of the downlink data cannot be transmitted on the failed antennas, which may cause decoding errors of the terminal and low rate. If the RRU synchronizes the antenna failure information to the MAC scheduler through the M surface, the maximum transmission layer number = min{M-X, N} is selected when performing downlink scheduling. Similarly, the BBU MAC also synchronizes the antenna failure information when performing resource allocation of the downlink CSI-RS reference signal, and the maximum antenna port number of the selected CSI-RS = min{M-X, N}, which can also improve the accuracy of the terminal measuring the reference signal.

[0039] Firstly, the application scenario of the SU-MIMO down-order transmission method provided by the embodiment of the present application is described. The method provided by the embodiment can be applied to the down-order auxiliary processing of MIMO in the downlink terminal SU-MIMO space division multiplexing transmission. For example, when part of the antennas of the RRU covering a certain cell fail, the downlink data cannot be transmitted on all the antennas, and part of the terminals have errors in the calculation of the received incomplete downlink reference signal measurement, and feedback the wrong RI and PMI information to the BBU, causing the failure of the downlink SU-MIMO down-order transmission.

[0040] By introducing the M surface device failure sensing between the RRU and the BBU, the BBU can comprehensively consider the channel quality feedback by the terminal and the actual bearing capacity of the device when performing scheduling, and can select the parameters conforming to the current transmission channel characteristics when performing SU-MIMO transmission, so as to ensure that the terminal can receive all the data and reference signals issued by the BBU, avoid the re-establishment and even the re-access process caused by the defects of the decoding algorithm of the terminal, and ensure the smooth switching of the downlink MIMO down-order transmission.

[0041] Each of the embodiments in the specification is described in a progressive manner, and the same and similar parts of each embodiment can be referred to each other. Especially for the device embodiment, the above description is only the preferred embodiment of the present application, and since it is basically similar to the method embodiment, it is described more simply, and the related parts can be referred to the part of the method embodiment. The above description is only the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any change or replacement that can be easily thought of by those skilled in the art within the technical range disclosed by the present application, and without departing from the principle of the present application, should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A MIMO order reduction assist method, characterized in that... Includes the following steps: 1) The BBU transmits the multi-antenna port CSI-RS reference signal through the RRU; 2) The terminal feeds back the CSI signal by measuring the CSI-RS reference signal. 3) The physical layer receives and parses the CSI signal fed back by the terminal and forwards it to the MAC layer; 4) The MAC scheduler performs SU-MIMO scheduling based on the information reported by the terminal; 5) The RRU detects a downlink transmit antenna failure and sends the information about the failed antenna to the OAM via the management plane M; 6) OAM synchronizes the fault information of the failed antenna to the MAC scheduler; 7) The MAC scheduler senses the status of the downlink transmit antennas. When performing downlink SU-MIMO scheduling, it integrates the CSI reported by the terminal and the actual number of available downlink antennas, and selects an appropriate RI / PMI to schedule the terminal. At the same time, the transmission of downlink CSI-RS is also adjusted according to the available downlink antennas to ensure that the number of antenna ports of CSI-RS is not greater than the number of downlink transmit antennas.

2. The MIMO order reduction assist method according to claim 1, characterized in that: Step 2) The CSI signal includes the rank indicator RI and the recommended precoding matrix PMI information.

3. The MIMO order reduction assist method according to claim 1, characterized in that: Assuming the RRU has M antennas for transmitting and receiving data, and the rank indicator RI value reported by the terminal is N, the maximum downlink transmission layer selected by the BBU during downlink SU-MIMO scheduling is min{M,N}.

4. The MIMO order reduction assist method according to claim 3, characterized in that: Assuming the RRU fails and X antennas are unable to transmit and receive data normally due to the failure, when performing downlink SU-MIMO scheduling in step 7), the maximum number of transmission layers is selected as min{MX,N}.

5. The MIMO order reduction assist method according to claim 3 or 4, characterized in that: Assuming the RRU fails, X antennas are unable to transmit and receive data normally due to the failure. In step 7), the transmission of downlink CSI-RS is synchronized with the antenna failure information. The maximum number of antenna ports selected for CSI-RS is min{MX,N}.

Images