CN101834642B - MIMO (Multiple Input Multiple Output) transmission method, base station device and communication system - Google Patents

Abstract

The invention discloses a multi-user MIMO (Multiple Input Multiple Output) transmission method, a base station device and a communication system. Aiming at a multi-user MIMO system adopting a precoding URS (Uniform Reporting System) as a demodulation reference signaling, the invention respectively provides a method for obtaining demodulation RD mapping modes from a plurality of user devices according to a plurality of URS multiplexing modes. The scheme is simple and effective and ensures that the multi-user MIMO system normally and efficiently works.

Description

Multiple-input multiple-output transmission method, base station equipment and communication system

technical field

The invention relates to the technical field of mobile communication, in particular to a method for multiple-input multiple-output (MIMO) transmission for multiple users by using user-based reference signaling (URS), a base station device and a communication system.

Background technique

Multiple Input Multiple Output (MIMO) technology has become one of the key technologies of the next generation wireless communication system. At present, there have been many studies on point-to-point single-user MIMO systems. In practical applications, the system often requires a base station to communicate with multiple user equipments at the same time, such as the most common cellular systems and wireless local area networks. Therefore, the research on point-to-multipoint multi-user MIMO (Multi-user MIMO) system emerges at the historic moment, which is more complicated than single-user MIMO.

Since the channels of each user in a multi-user MIMO system are independent of each other, a user can generally know its own channel state information, but it is difficult to obtain the channel information of other users, and obtaining the channel information of other users requires a great price. That is to say, it is difficult for users to collaborate. On the contrary, the base station has the conditions to obtain the channel state information of all communication users. For the time division duplex system, this can be obtained from the uplink reference signaling received by the base station, and for the frequency division duplex system, it needs to be obtained through feedback. In addition, the processing capability of the base station is much stronger than that of the user equipment. Therefore, the base station generally performs signal preprocessing (such as beamforming) before transmitting the signal to eliminate and suppress interference or perform post-processing after receiving the signal. Differentiate users. The multi-user MIMO technology has been successfully used in the LTE standard, and it can be predicted that it will also be one of the very important technologies in the LTE-Advanced system.

3GPP defines in its latest standardized document 3GPP TR36.913 (3GPP TSG RAN requirements for further advancements for E-UTRA, V8.0.0, 2008-06) that the LTE-Advanced system needs to support a maximum of 8×8 antenna configurations, that is, It is said that the base station equipment of the LTE-Advanced system is equipped with 8 antennas, which can support the transmission of 8-layer data streams at most at the same time. In the LTE system, however, the base station can support a maximum of 4×4 antenna configurations, and can support the transmission of 4-layer data streams at most at the same time. At the same time, the LTE standard defines a specific mapping mode of the downlink common reference signaling for each actual antenna port, and the LTE user equipment performs channel estimation and demodulation of received data according to the common reference signaling. In order to be forward compatible with LTE user equipment, the LTE-Advanced system must retain the common reference signaling defined in the existing LTE system. At the same time, in order to support the transmission of a maximum of 8 antennas, it is necessary to introduce additional reference signaling for corresponding data demodulation .

Currently, 3GPP RAN1 is discussing the design of 8-antenna reference signaling in the LTE-Advanced system. At the 56th RAN1 meeting held in Athens in February 2009, many companies reached a certain consensus on the design of downlink reference signaling and wrote it into the proposal R 1-091085 (Ericsson, Text proposal on DL reference signals, RAN1 #56, Athens, Greece, Feb.09-13, 2009). This proposal proposes to divide the downlink reference signaling in the LTE-Advanced system into two types, one is used for demodulation of downlink data, that is, the demodulation reference signaling, and the other is used for the measurement of the downlink channel state, namely Measurement reference signaling; the structure of downlink reference signaling needs to be able to support a variety of LTE-Advanced transmission characteristics, such as multi-point cooperative transmission (CoMP, CoordinatedMultipoint Transmission/Reception), spatial division multiplexing (SM, SpatialMultiplexing) and other transmissions model. The proposal further clarifies the demodulation reference signaling, which points out that the demodulation reference signaling is a precoded (precoded) user-based (UE-specific) reference signaling, and only exists when the base station is In the resource block scheduled by the user equipment, reference signaling on different layers (flows) should be orthogonal to each other. The proposal also supplements the design principles of reference signaling, and believes that the demodulation reference signaling of the LTE-Advanced system can look at the dedicated reference signaling (Dedicated RS) defined for LTE Rel-8 to support multiple layers (streams) An extension of transmission, and the measurement reference signaling used for channel quality indicator (CQI, Channel Quality Indicator) estimation is based on the cell-specific (Cell-specific) common reference signaling, and the common reference signaling on each antenna defined by LTE Compared with time-frequency domain, it can occupy relatively sparse resources.

Figure 1 shows the system model of the multi-user MIMO transmission mode defined in the existing LTE. The base station of the communication system as shown in Fig. 1 includes channel coding units 101 and 102, modulation units 103 and 104, scheduler 15, precoder 106, user grouping unit 107, common reference signaling loading units 108a-d, etc.

As shown in FIG. 1 , the channel coding units 101 and 102 perform channel coding on the bit stream of the user equipment by using Turbo coding or convolutional coding. The modulation units 103 and 104 modulate the channel-coded bits into OFDM symbols according to the channel quality. The user pairing unit 107 performs multi-user pairing according to the PMI/CQI/RI information fed back by the user equipment. The scheduler 105 schedules and allocates resources to the paired user equipments according to the feedback information from the user equipments. The precoder unit 106 performs a precoding operation on the data of each layer of each user equipment. The common reference signaling loading unit 108 loads common reference information on each antenna port according to a corresponding mapping mode.

As shown in Figure 1, the base station equipment of the LTE system is equipped with four antennas. According to the definition in the standard, each antenna is equipped with a common reference signaling based on a cell, and the time-frequency occupied by the common reference signaling on each antenna is The resource blocks are orthogonal to each other.

As shown in FIG. 1 , CRS ₀ to CRS ₃ represent the common reference signaling loaded on antenna port 0 to antenna port 3 respectively. LTE user equipment performs measurement through the common reference signaling (CRS ₀ ~ CRS ₃ ) on each antenna port, obtains downlink channel information, and feeds back the information to the base station equipment through the uplink channel (including uplink control channel and uplink shared channel). Information such as precoding matrix information (PMI, PrecodingMatrix Information), channel quality indicator (CQI, Channel Quality Indicator) and rank indicator (RI, Rank Indicator) obtained through calculation of the acquired downlink channel information. The user pairing unit 107 and the scheduler 105 of the base station equipment perform user pairing operations according to the received related information fed back by users, and perform related resource scheduling and allocation.

As shown in FIG. 1, if user equipment 0 and user equipment 1 are successfully paired, the scheduler 105 of the base station equipment allocates the same time-frequency resource block for the pair of user equipments, and the data information of the two user equipments is paired by the precoder 106. The respective precodings are mapped to different layers. As stipulated in the LTE standard, a user equipment performing multi-user MIMO transmission can only transmit one layer of data. Therefore, the base station in FIG. 1 transmits two layers of data at the same time, one layer is for user equipment 0, and the other layer is for user equipment 1. The base station transmits respective precoding information (PMI) to each user equipment through the downlink control channel, and the user equipment transmits the common reference signaling (CRS ₀ ~CRS ₃ ) loaded by the common reference signaling loading unit 108a-d on each antenna Perform channel estimation and receive the precoding information sent by the base station at the same time, combined with the estimated downlink channel information and the precoding information obtained from the base station, the received data can be demodulated, and the data transmitted by the base station can be correctly obtained information.

Single-stream beamforming (Beamforming) transmission is one of the transmission modes defined in the LTE standard. The LTE-Advanced system must also support this transmission mode, and may even need to support more advanced multi-stream multi-user beamforming transmission. Datang Mobile and Nortel are respectively in proposal R1-090185 (R1-090185, CATT, Dual ports DRSdesign for BF, RAN1#55bis, Ljubljana, Slovenia, Jan 12-16, 2009) and R 1-090754 (R1-090754 , Nortel, Performance evaluation of DRS design for multi-layer transmission, RAN1#56, Athens, Greece, Feb.09-13, 2009), the multiplexing scheme of multi-port dedicated reference signaling (Dedicated RS) is divided into two categories , one is a multiplexing scheme based on frequency division, which refers to the DRS transmission for different layers of data demodulation on different resource elements (RE, Resource Element); the other is a multiplexing scheme based on code division, It means that DRS used for data demodulation of different layers are transmitted on the same resource unit, and are distinguished by different orthogonal codes. Nortel also conducted a link-level simulation on the above two schemes in the proposal R1-090754. According to the simulation data, it can be known that the DRS multiplexing scheme based on frequency division can provide similar or even better performance than the DRS multiplexing scheme based on code division. good performance. If the user equipment has high mobility or the channel is dispersed in the frequency domain, the performance of the code-division-based DRS multiplexing scheme will drop sharply, because the orthogonality of the orthogonal codes loaded on different DRS will be destroyed . The proposal also points out that further research is yet to be done on the mapping mode (pattern) of the DRS.

In addition, ZTE pointed out in the proposal (R1-090636, ZTE, Consideration on Multi-user beamforming, RAN1#56, Athens, Greece, Feb.09-13, 2009) that multi-user beamforming that supports multiple streams may have a negative impact on standardization. Impact, which mentions three points, the first point is that it may be necessary to define new user-based reference signaling, because LTE Rel8 only defines the dedicated reference signaling on antenna port 5 as a solution to the single-user single-stream beamforming transmission mode Modulation reference signaling, for multi-stream multi-user beamforming, it is necessary to add demodulation reference signaling of the new antenna port through frequency division multiplexing (FDM) or reuse the antenna port 5 through code division multiplexing (CDM) The second point is the need to define new control signaling, including downlink control information (DCI) format, CQI feedback mode, rank (Rank) mode, etc.; the third point is the need for downlink shared channel (PDSCH) A new transmission mode is defined because the LTE standard does not support multi-stream multi-user beamforming transmission. Although the proposal raises a number of existing problems, it does not provide corresponding specific solutions.

Contents of the invention

The purpose of the present invention is to propose a method for multiple-input multiple-output (MIMO) transmission for multiple user equipments using user-based reference signaling (URS), as well as corresponding base station equipment and communication systems, which allow users to The device uses a specific URS mapping mode for channel estimation and data demodulation.

In one aspect of the present invention, a method for multiple-input multiple-output (MIMO) transmission for multiple users using user-based reference signaling (URS) is proposed, including: grouping of user equipment; determine the number of layers for each user equipment to transmit data at the same time and the corresponding URS mapping mode of multiple URS multiplexed for each layer; inform the user equipment of the URS mapping mode used and other URS mapping modes used by the user equipment through signaling. The number of layers of data is received; the URS and user data are precoded; and the precoded URS and user data are transmitted to the user equipment.

In another aspect of the present invention, a base station device is proposed, including: a grouping unit, which groups the multiple user equipments according to the information fed back from the user equipments; a scheduling unit, which determines the time for each user equipment to transmit data at the same time The number of layers and the URS mapping mode in which multiple URSs are multiplexed corresponding to each layer; the precoding unit precodes the URS and user data; and the transceiver unit informs the user equipment of the URS mapping mode it uses through signaling and the number of layers it receives data from, and transmits the precoded URS and user data to the user equipment.

Through the solution of the embodiment of the present invention, the user equipment can correctly know the URS mapping mode it adopts, so that it can perform correct channel estimation and data demodulation. The solution of this embodiment of the present invention is simple and effective, and can ensure the normal and efficient operation of the communication system.

Description of drawings

The above-mentioned and other purposes, features and advantages of the present invention will be made clearer by illustrating preferred embodiments of the present invention in conjunction with the accompanying drawings below, wherein:

Fig. 1 is the system model of the multi-user MIMO transmission mode defined in the existing LTE;

FIG. 2 is a system model of a multi-user MIMO transmission mode according to an embodiment of the present invention;

FIG. 3 is a process of multi-user MIMO transmission according to an embodiment of the present invention;

FIG. 4 is a resource unit mapping mode based on user reference signaling according to an embodiment of the present invention;

Fig. 5 is the mapping mode of frequency division multiplexing two URS;

Fig. 6 is the mapping mode of frequency division multiplexing three URS;

Fig. 7 is the mapping pattern of frequency division multiplexing four URS;

Figure 8 is a mapping mode of code division multiplexing two URS;

Figure 9 is a mapping mode of code division multiplexing four URS;

Figure 10 is a mapping mode of frequency division multiplexing plus code division multiplexing two URS;

Fig. 11 is a mapping mode of frequency division multiplexing plus code division multiplexing of four URSs.

Detailed ways

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, details and functions unnecessary to the present invention are omitted in order to prevent confusing understanding of the present invention.

In order to clarify and describe the implementation steps of the present invention in detail, specific embodiments of the present invention are given below, which are applicable to various mobile communication systems supporting multi-user MIMO transmission, especially LTE-Advanced cellular mobile communication systems. It should be noted that the present invention is not limited to these applications, but is applicable to more other related communication systems.

According to an embodiment of the present invention, a precoded (precoded) user-based reference signaling (URS, UE-specific RS) may be used as a downlink demodulation reference signaling in an LTE-Advanced system.

FIG. 2 shows a model of a multi-user MIMO transmission system using a precoded URS as a demodulation reference signal according to an embodiment of the present invention.

As shown in Figure 2, the base station in the communication system according to the embodiment of the present invention includes channel coding units 201 and 202, modulation units 203 and 204, user grouping unit 206, scheduler 205, URS loading units 207a and 207b and precoding device 208.

As shown in FIG. 2 , the channel coding units 201 and 202 channel code the bit streams of user equipment 0 and user equipment 1 by using turbo coding or convolutional coding. The modulation units 203 and 204 modulate the channel-coded bits into OFDM symbols according to the channel quality. The user grouping unit 206 performs multi-user grouping according to the PMI/CQI/RI information fed back by the user equipment, for example, user equipment 0 and user equipment 1 are configured in the same group.

In addition, the scheduler 205 performs operations such as scheduling and allocating resources to the user equipments paired in the same group according to the feedback information from the user equipments. The URS loading units 207a and 207b insert a URS on each layer of data of each user equipment.

The precoder 208 performs a precoding operation on the data of each layer of each user equipment and its URS.

As shown in Figure 2, the base station equipment in the LTE-Advanced system is equipped with eight antennas. Similar to the LTE system, each antenna will be equipped with common reference signaling for downlink measurement. The specific common reference signaling design can reuse the resources occupied by the common reference signaling used on the 4 antennas defined in LTE by reducing the density of the common reference signaling. Since the measurement reference signaling has nothing to do with this embodiment, here No specific description is given here. The LTE-Advanced user equipment performs measurement through the above common reference signaling, obtains downlink channel information, and feeds back information such as PMI, CQI, and RI calculated based on the obtained downlink channel information to the base station equipment through the uplink channel.

The user grouping unit 206 and the scheduling unit 205 of the base station equipment perform user grouping operations according to received relevant information fed back by users, and perform related operations such as resource scheduling. As shown in FIG. 2, if user equipment 0 and user equipment 1 are paired successfully, the scheduler 205 of the base station equipment allocates the same time-frequency resource block for the pair of user equipments, and passes the data information of the two user equipments through respective preset After encoding, it is mapped to different layers.

For the multi-user MIMO transmission mode in the LTE-Advanced system, each LTE-Advanced user equipment can receive data information of more than one layer at the same time. In this embodiment, one layer or two layers are taken as an example. The scheduler 205 of the base station equipment selects a URS mapping mode for the user equipment according to certain rules, and the precoding unit 208 uses the precoding used by the data of each layer of the user equipment to preprocess the reference signaling of the corresponding data layer and then map it to the corresponding On the resource unit corresponding to the URS mapping mode selected by the layer. The transceiver unit (not shown) of the base station equipment notifies the user equipment of the URS mapping mode it uses and the number of layers it receives data through corresponding signaling. The user equipment performs channel estimation according to the URS on each layer, so as to demodulate the data information on the corresponding layer.

In order to more clearly describe the process of multi-user MIMO transmission in the above-mentioned LTE-Advanced system, the steps are further described in conjunction with Figure 3. The specific implementation steps can be described as follows:

In step S1: the base station equipment transmits common measurement reference signaling to each user equipment on each antenna. The specific design of the common measurement reference signaling can be reused on the 4 antennas defined in LTE by reducing the density of the common reference signaling. The resources occupied by the common reference signaling are implemented;

In step S2: the user equipment detects the public measurement reference signaling to obtain downlink channel information, and calculates information such as CQI, PMI, and RI;

In step S3: the user equipment feeds back the calculated CQI, PMI and RI information to the base station equipment through the uplink channel;

In step S4: The user grouping unit 206 of the base station equipment performs multi-user pairing according to the relevant information fed back by the user, and the scheduler 205 determines the number of layers for each user equipment to transmit data at the same time and the URS mapping mode corresponding to each layer and performs resource allocation. Scheduling, allocating the same time-frequency resource block for the paired user equipment;

In step S5: the URS loading units 207a and 207b load respective URSs on the data streams of user equipment 0 and user equipment 1, and then, for example, the precoder 208 adopts the precoding used by the data of each layer of the user equipment to reference signaling of the corresponding data layer Perform preprocessing, and then map the preprocessed reference signaling to resource elements corresponding to the URS mapping mode selected for the corresponding data layer.

In step S6: the base station equipment notifies the user equipment of the URS mapping mode it uses and the number of layers it receives data through corresponding signaling;

In step S7: the base station equipment transmits the precoded URS and user data to the user equipment;

In step S8: the user equipment performs channel estimation according to the received URS, and uses the estimation result to perform data demodulation on the user data.

It should be specially pointed out that in step S6, different downlink control information (DCI, Downlink Control Information) formats can be used to distinguish the layer number of data received by the user equipment. Assuming that the user equipment supports multi-user MIMO transmission of two-layer data at most at the same time, DCI format A can be defined as a format for one-layer data transmission, and DCI format B can be defined as a format for two-layer data transmission. The user equipment performs blind detection on the downlink control channel. If DCI format A is detected, it means that the user equipment only transmits one layer of data, and according to the definition of the specific field indicating the URS mapping mode in the DCI, the user equipment adopts URS mapping mode; if DCI format B is detected, it means that the user equipment transmits two layers of data at the same time, and according to the definition of the specific field in the DCI indicating the URS mapping mode, two URS mappings corresponding to the two layers of data of the user equipment are obtained model.

The definition of the specific field indicating the URS mapping mode above needs to be determined according to the multiplexing scheme of the URS in the system. The definitions of different fields adopted by different URS multiplexing schemes will be described one by one below.

The resource element (RE, Resource Element) mapping mode of dedicated reference signaling (DRS, Dedicated RS) used for beamforming (Beamforming) transmission is defined in the LTE system, as shown in FIG. 4 . The resource units covered by oblique lines in the figure are cell-specific reference signaling (CRS, Cell-specific RS), and the resource units covered by gray colors in the figure are defined to transmit user-based DRS. Each physical resource block (PRB , PhysicalResource Block) blocks reserve 12 REs for DRS transmission.

Based on the DRS mapping mode in LTE shown in FIG. 4 , the multiple URS multiplexing mapping mode can be obtained in a frequency division multiplexing manner. As shown in FIG. 5 , two multiplexed URSs are represented by R5 and R6 respectively, and each URS occupies 12 REs in each PRB as defined in LTE. As the number of multiplexed URSs increases, the RE resource overhead occupied by them will increase significantly. Therefore, under certain circumstances, the density of URSs can be appropriately reduced under the premise of ensuring a certain performance. Figure 6 shows the resource mapping mode of three URS multiplexing. In the case of occupying 24 RE resources, the density of each URS is reduced to occupy 8 REs on each PRB. Similarly, Figure 7 shows the resource mapping mode of four URS multiplexing, where each URS occupies 8 REs on each PRB. In a word, when designing the multiplexed mapping mode of multiple URSs, it may be considered to appropriately reduce the density of resources occupied by each URS as the number of multiplexes increases, so as to ensure that the signaling overhead of URSs is within a controllable range.

Based on the above solution, the base station can select an appropriate URS multiplexing mode to perform URS mapping according to the multi-user pairing and the allocation of the transmission layers of each user. For example, when the user grouping unit 206 of the base station equipment pairs two user equipments and each user equipment transmits in a single layer, the precoder 208 of the base station equipment will adopt the mapping mode of two URS multiplexing as shown in FIG. 5 URS resource mapping is performed, and the user equipment needs to further know which mode (R5 or R6) to use to receive URS information after knowing the mapping mode in FIG. 5 . If the user grouping unit 206 of the base station equipment is paired with two user equipments and each user equipment transmits in two layers, the precoder 208 of the base station equipment will use the four URS multiplexing mapping modes shown in FIG. 7 for each Each layer of a user performs URS mapping, and the user equipment needs to know the specific mode (R0, R1, R2 or R3) adopted by each layer after knowing that it is two-layer transmission and adopts the mapping mode in Figure 7 to receive each layer Corresponding URS information. Combined with the multi-URS multiplexing scheme described above, the above-mentioned specific field indicating the URS mapping mode is defined as two parts, one part indicates the number of URS multiplexing layers, and its length is related to the maximum number of URS multiplexing layers defined by the system. If the system defines The maximum number of multiplexing layers is limited to 8 layers, so 3 bits are required to indicate the number of URS multiplexing layers; the other part indicates the index number of the URS mapping mode used by each layer, and its length is the same as the maximum number of URS multiplexing layers defined by the system and the user equipment The actual number of transmission layers is related. When the maximum number of multiplexing layers defined by the system is limited to 8 layers, if the user equipment transmits one layer of data, it needs 3 bits for indexing, and if the user equipment transmits two layers of data, it needs 6 bits for indexing , each layer is indicated by 3 bits.

Based on the DRS mapping mode in LTE shown in FIG. 4 , another frequency division multiplexing method can be used to obtain a multiple URS multiplexing mapping mode. As shown in Figure 7, a mapping mode of the maximum number of URS multiplexing layers supported by the system is fixed. In the figure, it is assumed that the maximum number of URS multiplexing layers is 4 layers, regardless of the number of users paired by the base station and the number of transmission layers scheduled. , both adopt the mapping mode shown in FIG. 7 to transmit the URS. When the base station equipment is paired with two users (user equipment A and user equipment B), and each user transmits in a single layer, R0 is used to transmit URS to user equipment A, and R1 is used to transmit URS to user equipment B. However, the RE resources occupied by R2 and R3 still need to be reserved and not be used to transmit any user data information. Based on the URS multiplexing method designed in this way, defining the above specific fields indicating the URS mapping mode only needs to indicate the index number of the URS mapping mode used by each layer, and its length is the same as the maximum number of URS multiplexing layers defined by the system and the user equipment. The actual number of transmission layers is related. When the maximum number of multiplexing layers defined by the system is limited to 8 layers, if the user equipment transmits one layer of data, it needs 3 bits for indexing, and if the user equipment transmits two layers of data, it needs 6 bits for indexing , each layer is indicated by 3 bits.

The multiplexing of multiple URSs can also be realized by way of code division multiplexing. As shown in Figure 8, two URSs (R0 and R1) can be multiplexed on the same time-frequency resource block through a pair of orthogonal codes. As shown in the figure, two URSs share 12 REs on one PRB to Complete the transfer. When the number of multiplexed URSs increases, the used time-frequency resource blocks can be appropriately increased to ensure multiplexed URS performance. As shown in FIG. 9 , a total of 24 REs with two symbols reserved on each PRB are used to transmit four URSs (R0, R1, R2, and R3), and the four URSs are distinguished by four orthogonal codes.

Based on the above design, the base station can select the appropriate time-frequency resource mapping mode and orthogonal code group according to the multi-user pairing and the allocation of each user's transmission layer. For example, when the base station pairs two user equipments and each user equipment transmits in a single layer, the base station equipment will use the time-frequency resource mapping mode shown in Figure 8 and a pair of corresponding orthogonal codes to multiplex two URS, and the user equipment After knowing that the time-frequency resource mapping mode in FIG. 5 is used, the device needs to further know which orthogonal code is used to receive the corresponding URS information. If the base station is paired with two user equipments and each user equipment performs two-layer transmission, the base station equipment will use the time-frequency resource mapping mode shown in Figure 9 to multiplex four URS, while the user equipment knows that it is two-layer transmission and adopts the After the time-frequency resource mapping mode shown in 9, it is necessary to further know the orthogonal code used by each layer to receive the corresponding URS information of each layer. Combined with the multi-URS multiplexing scheme based on code division multiplexing described above, the above-mentioned specific field indicating the URS mapping mode can be defined as two parts, one part indicates the time-frequency resource mapping mode and the orthogonal code group used, and its length is the same as It is related to the maximum number of URS multiplexing layers defined by the system. If the maximum number of multiplexing layers defined by the system is limited to 8 layers, 3 bits are required to indicate the corresponding information; the other part indicates the index number of the orthogonal code used by each layer of URS, Its length is related to the maximum number of URS multiplexing layers defined by the system and the actual number of transmission layers of the user equipment. When the maximum number of multiplexing layers defined by the system is limited to 8 layers, if the user equipment transmits one layer of data, it needs 3 bits to index , if the user equipment transmits two layers of data, 6 bits are needed for indexing, and each layer is indicated by 3 bits.

Another way of code division multiplexing can also be used to multiplex multiple URSs. As shown in Figure 9, a time-frequency mapping mode with the maximum number of URS multiplexing layers supported by the system is fixed. In the figure, it is assumed that the maximum number of URS multiplexing layers is 4 layers, regardless of the number of users paired by the base station and the number of transmission layers scheduled The URS is multiplexed using the time-frequency mapping mode shown in FIG. 9 . When the base station equipment pairs two users (user equipment A and user equipment B), and each user transmits in a single layer, use the orthogonal code corresponding to R0 to transmit URS to user equipment A, and use the orthogonal code corresponding to R1 to transmit URS to user equipment B transmits URS. When the base station equipment pairs three users (user equipment A, user equipment B, and user equipment C), and each user transmits in a single layer, use the orthogonal code corresponding to R0 to transmit URS to user equipment A, and use the orthogonal code corresponding to R1 The code transmits the URS to the user equipment B and uses the orthogonal code corresponding to R2 to transmit the URS to the user equipment C.

Based on the URS multiplexing method designed in this way, the definition of the specific field indicating the URS mapping mode above only needs to indicate the index number of the orthogonal code used by each layer, and its length is the same as the maximum number of URS multiplexing layers defined by the system and the user equipment. The actual number of transmission layers is related. When the maximum number of multiplexing layers defined by the system is limited to 8 layers, if the user equipment transmits one layer of data, it needs 3 bits for indexing, and if the user equipment transmits two layers of data, it needs 6 bits for indexing , each layer is indicated by 3 bits.

Multiplexing multiple URSs can also be implemented by frequency division multiplexing plus code division multiplexing. The basic principle is to adopt the scheme of frequency division multiplexing when few URSs are multiplexed, and to adopt the scheme of code division multiplexing on the basis of frequency division multiplexing when more URSs are multiplexed. As shown in Figure 10, when only two URSs are multiplexed, each URS (R0 and R1) occupies 12 mutually orthogonal RE resources for transmission without loading any orthogonal code. When four URSs are multiplexed, as shown in Figure 11, two URSs are simultaneously transmitted through two orthogonal codes on the RE resources occupied by one URS as shown in Figure 10, so that the resource usage remains unchanged. , which can expand the number of URS multiplexing. For user equipment with high movement speed, the URS they use can work in frequency division multiplexing by limiting the number of paired user equipment, which can effectively resist the orthogonality of the orthogonal code that may be caused by the fast fading of the channel. Sexual sabotage problem.

Based on the above-mentioned URS multiplexing scheme, its signaling structure can be divided into two parts. The first part is the group indicator bit. If the multiplexing mode is frequency division multiplexing, the group indicating bit indicates the number of URS multiplexing layers. If the multiplexing mode For frequency division multiplexing plus code division multiplexing, this group of indication bits indicates the time-frequency resource mapping mode and the orthogonal code group used. According to this group of indication bits, it can be implicitly known whether to use frequency division multiplexing or frequency division Multiplexing plus code division multiplexing; the third part is the index indication bit within the group. If it is frequency division multiplexing, it indicates the index number of each layer using URS mapping mode. If it is frequency division multiplexing plus code division multiplexing, the Indicates the index number of the orthogonal code used by the URS of each layer of bits.

Through the scheme for implementing multi-user MIMO transmission proposed above by using URS, normal transmission of multi-user MIMO can be realized. The complexity of the system is low, which meets the requirements of the actual system and the LTE-Advanced system.

So far the invention has been described with reference to the preferred embodiments. It should be understood that various other changes, substitutions and additions can be made by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the scope of the present invention is not limited to the specific embodiments described above, but should be defined by the appended claims.

Claims (22)

1. A method for multiple-input multiple-output (MIMO) transmission for multiple users using user-based reference signaling (URS), comprising: performing grouping on the plurality of user equipments according to the information fed back from the user equipments; Determine the number of layers for each user equipment to transmit data at the same time and the corresponding URS mapping mode for multiple URSs to be multiplexed for each layer; Informing the user equipment of the URS mapping mode it uses and the number of layers it receives data through signaling; precoding URS and user data; and The precoded URS and user data are transmitted to the user equipment. 2. The method according to claim 1, wherein the step of precoding URS and user data comprises: Preprocessing the reference signaling of the corresponding data layer by using the precoding used by the data of each layer of the user equipment; The preprocessed reference signaling is mapped to the time-frequency resource unit corresponding to the URS mapping mode selected for the corresponding data layer. 3. The method according to claim 1, wherein the user equipment performs channel estimation according to the received URS, and uses the channel estimation result to perform data demodulation on the received user data. 4. The method according to claim 1, wherein different downlink control information formats are used to distinguish the number of layers at which the user equipment receives data. 5. The method according to claim 1, wherein a plurality of URSs are multiplexed by means of frequency division multiplexing, and the field indicating the URS mapping mode comprises: a first part indicating the number of URS multiplexing layers; and a second part, Indicates the index number of the URS mapping mode used by each layer. 6. The method according to claim 5, wherein, adopting frequency division multiplexing to realize multiple URS multiplexing, and reducing the density of time-frequency resources occupied by each URS as the number of URS multiplexing increases, to ensure The signaling overhead of URS is within the specified range. 7. The method according to claim 1, wherein frequency division multiplexing is used to implement multiple URS multiplexing, and the field indicating the URS mapping mode indicates the index number of each layer adopting the URS mapping mode. 8. The method according to claim 1, wherein a plurality of URSs are multiplexed by means of code division multiplexing, and the field indicating the URS mapping mode comprises: a first part indicating the time-frequency resource mapping mode and the orthogonality used by it a code group; and a second part indicating an index number of an orthogonal code adopted by each layer. 9. The method according to claim 8, wherein when the number of multiplexed URSs increases, the performance of code division multiplexing of multiple URSs is ensured by increasing the used time-frequency resource units. 10. The method according to claim 1, wherein multiple URSs are multiplexed by means of code division multiplexing, and the field indicating the URS mapping mode indicates the index numbers of the orthogonal codes used by each layer. 11. The method according to claim 1, wherein multiple URSs are multiplexed using frequency division multiplexing plus code division multiplexing, and the field indicating the URS mapping mode includes a first part and a second part: the first part is a group indication Bits, if the multiplexing method is frequency division multiplexing, the group of indicating bits indicates the number of URS multiplexing layers; if the multiplexing method is frequency division multiplexing plus code division multiplexing, the group indicating bits indicates the time-frequency resource mapping mode and The orthogonal code group used by it, whether the specific URS multiplexing method is frequency division multiplexing or frequency division multiplexing plus code division multiplexing can be implicitly indicated by the group indicating bits; the second part is the group index indicating bits, if it is For frequency division multiplexing, it indicates the index number of the URS mapping mode used by each layer. If it is frequency division multiplexing plus code division multiplexing, the indicator bit indicates the index number of the orthogonal code used by the URS of each layer. 12. A base station device, comprising: a grouping unit, configured to group the plurality of user equipments according to information fed back from the user equipments; The scheduling unit determines the number of layers for each user equipment to transmit data at the same time and the URS mapping mode in which multiple user-based reference signaling (URS) is multiplexed corresponding to each layer; a precoding unit to precode URS and user data; and The transceiver unit informs the user equipment of the URS mapping mode it uses and the number of layers it receives data through signaling, and transmits the precoded URS and user data to the user equipment. 13. The base station device according to claim 12, wherein the precoding unit preprocesses the reference signaling of the corresponding data layer by using the precoding used by the data of each layer of the user equipment, and converts the preprocessed reference signaling It is mapped to the time-frequency resource unit corresponding to the URS mapping mode selected for the corresponding data layer. 14. The base station device according to claim 12, wherein different downlink control information formats are used to distinguish the number of layers of data received by the user equipment. 15. The base station device according to claim 12, wherein frequency division multiplexing is used to realize multiple URS multiplexing, and the field indicating the URS mapping mode includes: a first part indicating the number of URS multiplexing layers; and a second part , indicating that each layer adopts the index number of the URS mapping mode. 16. The base station device according to claim 15, wherein frequency division multiplexing is used to realize multiple URS multiplexing, and as the number of URS multiplexing increases, the density of time-frequency resources occupied by each URS is reduced, so as to Ensure that the signaling overhead of the URS is within the specified range. 17. The base station device according to claim 12, wherein frequency division multiplexing is used to implement multiple URS multiplexing, and the field indicating the URS mapping mode indicates the index number of each layer adopting the URS mapping mode. 18. The base station device according to claim 12, wherein multiple URSs are multiplexed using code division multiplexing, and the field indicating the URS mapping mode includes: a first part indicating the time-frequency resource mapping mode and the normal an orthogonal code group; and a second part indicating the index number of the orthogonal code adopted by each layer. 19. The base station device according to claim 18, wherein when the number of multiplexed URSs increases, the performance of code division multiplexing of multiple URSs is ensured by increasing the used time-frequency resource units. 20. The base station device according to claim 12, wherein multiple URSs are multiplexed by means of code division multiplexing, and the field indicating the URS mapping mode indicates the index numbers of the orthogonal codes used by each layer. 21. The base station device according to claim 12, wherein frequency division multiplexing plus code division multiplexing is used to realize multiple URS multiplexing, and the field indicating the URS mapping mode includes a first part and a second part: the first part is group Indication bits, if the multiplexing mode is frequency division multiplexing, the group of indication bits indicates the number of URS multiplexing layers, if the multiplexing mode is frequency division multiplexing plus code division multiplexing, the group of indication bits indicates the time-frequency resource mapping mode And the orthogonal code group used, whether the specific URS multiplexing method is frequency division multiplexing or frequency division multiplexing plus code division multiplexing can be implicitly indicated by the group indicating bits; the second part is the group index indicating bits, if If it is frequency division multiplexing, it indicates the index number of the URS mapping mode used by each layer. If it is frequency division multiplexing plus code division multiplexing, this indicates the index number of the orthogonal code used by the URS of each layer. 22. A communication system, comprising the base station equipment according to any one of claims 12 to 21, and a user terminal, the user terminal performs channel estimation according to the received user-based reference signaling (URS), and utilizes the channel The estimated result performs data demodulation on the received user data.

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