Heterogeneous network joint multi-antenna transmission architecture based on cu and du separation

Abstract

The application provides a CU and DU separated heterogeneous network joint multi-antenna transmission architecture, wherein the CU and DU are separated at the base station end, the transmission architecture comprises a broadcast large tower network and a cellular network with heterogeneous networks, the broadcast large tower network and the cellular network are both provided with multi-antenna transmission, data transmitted by the broadcast large tower network and the cellular network is distributed through a CDN network, and broadcast, multicast and unicast services are jointly transmitted, the transmission module and the resource distribution module in the system are designed at the architecture level, the functional modules are realized, the system diversity gain is improved through the multi-antenna transmission design of the base station, a precoding scheme is designed for different service transmission types, system data flow is mapped to the transmitting antenna, the physical layer bandwidth and power resource distribution of the transmission system is researched, and the sum rate of the system unicast transmission is maximized under the condition of guaranteeing the broadcast and multicast transmission rate.

Description

Technical Field

[0001] This invention relates to the field of information dissemination technology, and in particular to a heterogeneous network joint multi-antenna transmission architecture based on the separation of CU and DU. Background Technology

[0002] Multimedia Broadcast Multicast Services (MBMS) enables a broadcast network within a specific area to simultaneously transmit point-to-multipoint services to multiple users. Traditional television broadcasting is based on a low carrier frequency band of 600MHz-700MHz, using large towers as the main transmitting base stations, with each tower employing a single antenna for transmission. In existing cellular networks, base stations operate in high carrier frequency bands (FR1: 450MHz-6000MHz, FR2: 24250MHz-52600MHz), employing massive MIMO (Multi-Match Multi-Antenna) to transmit unicast signals.

[0003] Relevant literature proposes a logical architecture for joint transmission of traditional broadcast towers and cellular base stations through a CDN virtual network, such as... Figure 1 As shown, broadcast content providers and OTT unicast content providers transmit data to the CDN network, coordinating and allocating the transmission of broadcast and cellular unicast services respectively through CDN servers configured within the region. However, the architecture does not utilize the existing base station-side CU and DU separation architecture.

[0004] 5GXcast proposes an architecture where the CU and DU are separated at the base station level within a homogeneous network architecture, such as... Figure 2 As shown, by adding a Centralized Unit MultiCast (MC) to the base station, the specific function of carrying broadcast services under 5G cellular network is realized. However, the architecture does not take into account the actual deployment of broadcast services in my country and is not designed based on multi-service transmission in heterogeneous networks. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to combine the actual deployment of broadcast services with the reasonable architecture design of the existing base station CU and DU separation. This invention proposes a heterogeneous network joint multi-antenna transmission architecture based on the separation of CU and DU.

[0006] According to an embodiment of the present invention, a heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation is characterized in that the transmission architecture separates CU and DU at the base station end, and the transmission architecture includes: a broadcast tower network and a cellular network with heterogeneous networks, both the broadcast tower network and the cellular network deploying multi-antenna transmission, and the data transmitted by the broadcast tower network and the cellular network are distributed through a CDN network to jointly transmit broadcast, multicast and unicast services.

[0007] According to some embodiments of the present invention, the broadcast service transmission of the broadcast tower network employs space frequency code precoding.

[0008] In some embodiments of the present invention, the CDN network server transmits the channel status information of the broadcast tower fed back by the user to the CU, performs space frequency code precoding at the CU, and transmits the encoded information to the RRU via the DU and sends it to the user.

[0009] According to some embodiments of the present invention, the cellular base station of the cellular network is divided into three carrier bandwidth portions, which are respectively used to transmit broadcast services of mobile users within the system that are more than a preset distance from the broadcast tower, transmit multicast services of all users within the system, and transmit unicast services of all users within the system.

[0010] In some embodiments of the present invention, space-time block coding is used for the broadcast service carrier bandwidth portion of the cellular base station, zero-breaking precoding is used for the multicast service carrier bandwidth portion of the cellular base station, and zero-breaking precoding is used for the unicast service carrier bandwidth portion of the cellular base station.

[0011] According to some embodiments of the present invention, in a cellular base station system, cells are clustered within a preset range, and all cellular base stations within the same cell cluster are classified as a cooperative unit. Transmission points located in the same cooperative unit cooperate to participate in the transmission or reception of user data within the corresponding cooperative unit.

[0012] In some embodiments of the present invention, for cell clusters where broadcast services are carried by cellular cells, open-loop MIMO precoding is used for precoding.

[0013] According to some embodiments of the present invention, a CU-MC module is added at a position parallel to the CU at the base station end to process multicast and broadcast user data. At the CU-MC module, the user broadcast service information that needs to be carried by the cellular network is precoded using space-time block codes. At the CU, user unicast information is precoded using ZF code, and multicast information is precoded using ZF code.

[0014] In some embodiments of the present invention, the transmission architecture feeds back the channel information of the user-selected access broadcast tower and cellular base station to the cellular base station via the FDD channel, and performs unified resource allocation through the CDN server.

[0015] The present invention has the following beneficial effects:

[0016] This invention designs the transmission module and resource allocation module within the system at the architectural level, implements the functional modules, improves the diversity gain of the system by adopting a multi-antenna transmission design for base stations, designs precoding schemes for different service transmission types, and maps the system data stream to the transmitting antennas. It also studies the allocation of physical layer bandwidth and power resources for the transmission system, maximizing the sum rate of unicast transmission while ensuring the broadcast and multicast transmission rates. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the logical architecture for joint transmission between broadcast towers and cellular base stations via a CDN virtual network in existing technologies.

[0018] Figure 2 This is a schematic diagram of the existing architecture where the CU and DU are separated at the base station in a homogeneous network architecture.

[0019] Figure 3 This is a schematic diagram of the network architecture for a solution based on broadcast towers and cellular base stations that enables joint broadcast, multicast, and unicast multi-service transmission.

[0020] Figure 4 A block diagram of an optimization algorithm for the transmission network framework in the prior art;

[0021] Figure 5 This is a schematic diagram of a heterogeneous network joint multi-antenna transmission architecture based on the separation of CU and DU according to an embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of the access network design for a broadcast tower according to an embodiment of the present invention;

[0023] Figure 7 This is a schematic diagram of a cooperative cellular base station access network design according to an embodiment of the present invention;

[0024] Figure 8 A flowchart illustrating a procedure for transmitting broadcast services via a broadcast tower according to an embodiment of the present invention;

[0025] Figure 9 A flowchart illustrating a procedure for transmitting broadcast services using a cellular base station according to an embodiment of the present invention. Detailed Implementation

[0026] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0027] The steps described in the specification and the flowcharts in the accompanying drawings of this invention are not necessarily to be strictly followed according to the step numbers; the execution order of the steps can be changed. Furthermore, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be broken down into multiple steps.

[0028] The relevant technical terms used in this invention are explained in the table below:

[0029]

[0030]

[0031] The existing network architecture for joint broadcast, multicast, and unicast multi-service transmission based on broadcast towers and cellular base stations is as follows: Figure 3 As shown. The broadcast tower operates at... Under the carrier frequency, the transmission power is high and the coverage is wide. Cellular base stations operate in Under the carrier frequency, the base stations are relatively densely distributed and the transmission power is low.

[0032] The broadcast tower's frequency domain is divided into two carrier bandwidth sections, BWP1. H and BWP1 H Configured with a large cyclic prefix and a small subcarrier spacing, it is responsible for carrying broadcast services for fixed or low-speed mobile users within the system. Configuration relative to BWP1 H A smaller cyclic prefix and a larger subcarrier spacing are used to carry broadcast services for high-speed mobile users closer to the tower. Broadcast services for high-speed mobile users at the tower's edge are carried by the cellular network. Cellular base stations are divided into three carrier bandwidth sections (BWP1). L , and They are configured with the same subcarrier spacing, and are respectively responsible for the transmission of broadcast services for high-speed mobile users who are far from the tower, the transmission of multicast services for all users in the system, and the transmission of unicast services for all users in the system.

[0033] The table below shows the user access selection criteria. Users can simultaneously receive signals from both broadcast towers and cellular base stations. If user k needs to apply for broadcast service access, it needs to consider its geographical location l. k and velocity v kSelective access to broadcast service frequency band resources from broadcast towers and cellular base stations, if the user's movement speed v k For speeds ≤67.5km / h, connect to tower BWP1. H Carrier bandwidth portion; if the user's moving speed is 67.5 km / h < v k ≤250km / h, and the area is l k ∈Cor near Then connect to the large tower. Regarding the carrier bandwidth, if the user's moving speed is 67.5 km / h < v k ≤250km / h, and the area is l k ∈Cor edge Then connect to Cor edge The carrier bandwidth portion of the cellular network broadcast service within the area. For multicast service reception, the terminal determines its location. k and movement speed v k Select the multicast service carrier bandwidth corresponding to the nearest base station. This enables multi-base station cooperative transmission. For unicast service reception, the user selects the unicast service carrier bandwidth portion of the nearest serving cellular base station. It also removes interference from adjacent base stations on the same subcarrier.

[0034]

[0035]

[0036] The above scheme simultaneously performs joint power allocation of power and bandwidth for broadcast, multicast, and unicast services in a heterogeneous network architecture. The optimization objective is to maximize the sum rate of unicast users within the system while ensuring the transmission rates of broadcast and multicast. The optimization algorithm block diagram is as follows: Figure 4 As shown:

[0037] To reduce the time complexity of the solution, an optimization problem-solving method based on a combination of genetic algorithms and convex optimization is used to solve the optimization problem of the large tower. The algorithm first uses a joint physical layer bandwidth and power allocation method based on genetic algorithms and convex optimization to find the maximum broadcast transmission rate achievable by the broadcast tower. Then, through analysis of the broadcast, multicast, and unicast service transmission modes of cellular base stations, it maximizes the sum of unicast transmission rates while ensuring the broadcast and multicast transmission rates. However, this scheme does not consider scenarios where macro and micro base stations are configured with multiple antennas; it only considers single-antenna transmission schemes.

[0038] Based on the background technology and the above description of the solution, it can be seen that the existing technology has the following defects:

[0039] 1. The logical architecture proposed in relevant literature for joint transmission between broadcast towers and cellular base stations under CDN network scheduling achieves joint service transmission between broadcast towers and cellular base stations. However, it does not consider the access network design of broadcast towers and cellular base stations under a CU and DU separation architecture at the base station end. 5GXcast proposes adding a Centralized Unit MultiCast (MC) to the base station end in a homogeneous cellular network, enabling the cellular network to carry broadcast / multicast services. However, it does not consider how to design the DU and CU separation mode and perform unified scheduling under a CDN network in a heterogeneous network architecture of broadcast towers and cellular base stations.

[0040] 2. In the existing broadcast, multicast, and unicast multi-service transmission and resource allocation schemes based on the heterogeneous network architecture of broadcast towers and cellular base stations, only the scenario where both the broadcast tower and the cellular base station have a single antenna is considered, resulting in low channel capacity.

[0041] 3. Since broadcast service is a one-to-many service without feedback, the base station is only responsible for transmitting the broadcast service. Whether there are users receiving the broadcast and how many users are receiving it are random. Therefore, closed-loop MIMO precoding schemes such as MRT and ZF, which estimate the channel at the receiver and feed it back to the transmitter for specific user channel state information, cannot be used in the precoding design of multi-antenna systems. Instead, open-loop MIMO precoding schemes such as Space-Time Code (STC), Space-Frequency Code (SFC), and Space-Time-Frequency Code (STFC) are required.

[0042] 4. Existing multi-service transmission and resource allocation schemes for broadcast, multicast, and unicast services based on heterogeneous network architectures of broadcast towers and cellular base stations only consider the physical layer bandwidth and power allocation schemes when both broadcast towers and cellular base stations are single-antenna transmission modes.

[0043] Considering the aforementioned literature and the architectural incompleteness of 5G Xcast, this paper first proposes a heterogeneous network transmission architecture based on the separation of CU and DU between broadcast towers and cellular base stations. Then, it configures multi-antenna transmission at both the broadcast tower and cellular base station ends of existing multi-service transmission systems deployed in heterogeneous networks, and designs different precoding schemes based on different service types. Finally, it analyzes the optimization problem of the proposed heterogeneous network multi-antenna system transmission mode.

[0044] According to an embodiment of the present invention, a heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation is characterized in that the transmission architecture separates CU and DU at the base station end, and the transmission architecture includes: a broadcast tower network and a cellular network with heterogeneous networks, both the broadcast tower network and the cellular network deploying multi-antenna transmission, and the data transmitted by the broadcast tower network and the cellular network are distributed through a CDN network to jointly transmit broadcast, multicast and unicast services.

[0045] According to some embodiments of the present invention, space frequency code precoding is used in the broadcast service transmission of the broadcast tower network.

[0046] In some embodiments of the present invention, the CDN network server transmits the channel status information of the broadcast tower fed back by the user to the CU, performs space frequency code precoding at the CU, and transmits the encoded information to the RRU via the DU and sends it to the user.

[0047] According to some embodiments of the present invention, the cellular base station of the cellular network is divided into three carrier bandwidth portions, which are respectively used to transmit broadcast services for high-speed mobile users within the system who are more than a preset distance from the broadcast tower, transmit multicast services for all users within the system, and transmit unicast services for all users within the system.

[0048] In some embodiments of the present invention, space-time block code precoding is used in the broadcast service carrier bandwidth portion of the cellular base station, zero-breaking precoding is used in the multicast service carrier bandwidth portion of the cellular base station, and zero-breaking precoding is used in the unicast service carrier bandwidth portion of the cellular base station.

[0049] According to some embodiments of the present invention, in a cellular base station system, cells are clustered within a preset range, and all cellular base stations within the same cell cluster are classified as a cooperative unit. Transmission points located in the same cooperative unit cooperate to participate in the transmission or reception of user data within the corresponding cooperative unit.

[0050] In some embodiments of the present invention, for cell clusters where broadcast services are carried by cellular cells, open-loop MIMO precoding is used for precoding.

[0051] According to some embodiments of the present invention, a CU-MC module is added at a position parallel to the CU at the base station end to process multicast and broadcast user data. At the CU-MC module, the user broadcast service information that needs to be carried by the cellular network is precoded using space-time block codes. At the CU, user unicast information is precoded using ZF code, and multicast information is precoded using ZF code.

[0052] In some embodiments of the present invention, the transmission architecture feeds back the channel information of the user-selected access broadcast tower and cellular base station to the cellular base station via the FDD channel, and performs unified resource allocation through the CDN server.

[0053] The present invention has the following beneficial effects:

[0054] This invention designs a multi-antenna transmission system for terrestrial broadcasting, multicast, and unicast services based on a CU and DU separation mode, where a broadcast tower and a cellular base station are combined. Combining the architecture of broadcast systems and cellular networks, the transmission module and resource allocation module within the system are designed at the architecture level, and the functional modules are implemented.

[0055] In the heterogeneous network transmission system of broadcast tower and cellular base station, this invention adopts a multi-antenna transmission design at the transmitting end of both the broadcast tower and the cellular base station, and a single-antenna receiving design at the user receiving end, thereby improving the diversity gain of the system.

[0056] This invention designs precoding schemes for different service transmission types at the broadcast tower and cellular base station transmitting ends, mapping the system data stream to the transmitting antenna;

[0057] This invention studies the allocation of physical layer bandwidth and power resources for the proposed multi-antenna transmission system combining broadcast towers and cellular base stations. The optimization objective is to maximize the sum of the system's unicast transmission rate while ensuring the system's broadcast and multicast transmission rates.

[0058] In summary, this invention, based on the design concept of DU and CU separation mode, designs a network architecture under the network architecture of joint heterogeneous transmission of broadcast tower and cellular base station. At the same time, it implements the specific algorithm function module of the multi-antenna joint transmission proposed in this invention.

[0059] This invention designs a transmission scheme for both broadcast towers and cellular base stations in scenarios where both have multiple antennas, thereby improving system capacity by using multi-antenna transmission.

[0060] This invention combines the differences in transmission modes between broadcast towers and cellular base stations, as well as the different types of broadcast, multicast, and unicast services, and designs open-loop MIMO precoding to map the original transmitted information to the antenna end. Through the design of open-loop MIMO precoding such as Space-Time Block Code (STBC) and Space-Frequency Code (SFC), the system achieves diversity gain in the spatial, temporal, and subcarrier dimensions.

[0061] Space Frequency Code (SFC) is used on the broadcast tower, Space Time Block Code (STBC) is used on the broadcast carrier bandwidth of the cooperative cellular base station, Zero-Forcing (ZF) precoding is used on the multicast carrier bandwidth, and Zero-Forcing (ZF) precoding is used on the unicast portion.

[0062] This invention combines different open-loop MIMO precoding design schemes for broadcast towers and cellular base stations, and performs a joint resource allocation design for physical layer bandwidth and power, maximizing the system's unicast transmission and rate while ensuring the broadcast and multicast transmission rates within the system.

[0063] The present invention has the following beneficial effects:

[0064] This invention designs a multi-antenna transmission system for terrestrial broadcasting, multicast, and unicast services based on a CU and DU separation mode, where a broadcast tower and a cellular base station are combined. Combining the architecture of broadcast systems and cellular networks, the transmission module and resource allocation module within the system are designed at the architecture level, and the functional modules are implemented.

[0065] In the heterogeneous network transmission system of broadcast tower and cellular base station, this invention adopts a multi-antenna transmission design at the transmitting end of both the broadcast tower and the cellular base station, and a single-antenna receiving design at the user receiving end, thereby improving the diversity gain of the system.

[0066] This invention designs precoding schemes for different service transmission types at the broadcast tower and cellular base station transmitting ends, mapping the system data stream to the transmitting antenna;

[0067] This invention studies the allocation of physical layer bandwidth and power resources for the proposed multi-antenna transmission system combining broadcast towers and cellular base stations. The optimization objective is to maximize the sum of the system's unicast transmission rate while ensuring the system's broadcast and multicast transmission rates.

[0068] The heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation according to the present invention is described in detail below with reference to the accompanying drawings. It is to be understood that the following description is merely exemplary and should not be construed as a specific limitation of the present invention.

[0069] I. A multi-antenna transmission architecture based on a heterogeneous network of broadcast towers and cellular base stations with separate CU and DU.

[0070] This invention proposes a multi-antenna transmission architecture that combines broadcast towers and cellular base stations in a CU and DU separation architecture, such as... Figure 5As shown, the broadcast tower network and cellular network are jointly transmitted under the cooperation of the CDN network. The CDN network distributes the data transmitted through the broadcast tower and the data transmitted through the cellular network. The access network design for the broadcast tower and the cellular network is also different.

[0071] like Figure 6 The diagram shows the access network design of the broadcast tower. The CDN server transmits the channel status information of the broadcast tower fed back by the user to the CU, then performs space frequency code (SFC) encoding at the CU, then transmits the encoded information to the DU, and then to the RRU to send it to the user.

[0072] like Figure 7 The diagram shows the design of a cooperative cellular base station access network. A CU-MC module is added at the base station end, parallel to the CU, to process multicast and broadcast user data. At the CU-MC, space-time block code (STBC) precoding is performed on the user broadcast service information that needs to be carried by the cellular network. At the CU, ZF precoding is performed on user unicast information and multicast information.

[0073] At the receiving end, users select different carrier bandwidth portions of the broadcast tower and cellular base station based on their location and movement speed. After channel estimation, the channel information is fed back to the cellular base station through the FDD channel, and then unified resource allocation is performed through the CDN server.

[0074] II. Scheme for joint multi-antenna transmission and resource allocation based on broadcast tower and cellular base station:

[0075] a) Multi-service transmission system model under heterogeneous network

[0076] This section introduces a multi-service transmission system model based on heterogeneous network deployment, and analyzes the system model separately based on the transmission characteristics of broadcast towers and cellular base stations and the different service types.

[0077] (a.1) Transmission model of the physical layer of the broadcast tower

[0078] In this model, let the number of broadcast towers be F. H The set of broadcast towers within the system is represented as The user set in the system is represented as Access tower BWP1 H The user set is represented as Access Tower The user set is represented as The set of towers whose signals transmitted from a broadcast tower to user k satisfy the distance range allowed by the cyclic prefix of the tower's physical layer is represented as follows: The number of antennas at the transmitting end of the broadcast tower is The user receiver uses a single antenna, and the broadcast tower's transmission bandwidth is B. H The carrier bandwidth portion BWP1 H and The bandwidth occupied is represented as α1B. H ,α2B H The subcarrier spacings are respectively and Carrier bandwidth section BWP1 H and The number of subcarriers is expressed as follows: The subcarrier sets are respectively represented as and Indicates the broadcast tower f H The channel parameter vector of user k on subcarrier n, Indicates the broadcast tower f H The channel parameters for user k on the i-th antenna of subcarrier n. The number of broadcast towers deployed in the area is relatively small, and the number of users receiving broadcast services is random. It is impossible to design specific transmitters for specific users based on user channel condition feedback. All towers use the same power allocation scheme to send broadcast service information to users within the area. and These represent the carrier bandwidth portion BWP1 allocated to the broadcast tower. H and On the power, Indicates will Subcarriers On power, Indicates will Subcarriers The power on.

[0079] Broadcast towers have a wide coverage area, and the number of users receiving broadcast services is random. Therefore, the precoding design for broadcast towers cannot be based on closed-loop precoding using channel state information from specific users; an open-loop MIMO precoding scheme is required. Broadcast towers use small subcarrier spacing, and the duration of an OFDM symbol is relatively long, so a space frequency code (SFC) precoding design is employed. Literature analysis shows that only when the number of antennas M... t The bitrate R will only be obtained when the value is 2. c A complex encoded orthogonal matrix with =1, when the number of antennas M t =3 or M t When the value is 4, the code rate can be obtained. A specific complex coding orthogonal matrix, at a code rate At this point, a complex coding orthogonal matrix with an arbitrary number of antennas can be obtained. Different complex coding orthogonal matrices correspond to different maximum ratio combining formulas at the receiver. This scheme uses the Alamouti space-frequency precoding scheme on the broadcast tower, with a transmitter antenna number... The broadcast tower transmitter transmits two codewords on two adjacent subcarriers, with a code rate R. c =1. The flowchart for transmitting broadcast services from the broadcast tower is as follows: Figure 8 As shown.

[0080] To ensure the correctness of the space-frequency code precoding dimension without loss of generality, the scheme design adopts... and All are integer multiples of 2. In the carrier bandwidth section BWP1 H The codewords that need to be transmitted on each subcarrier are represented as follows: If two adjacent subcarriers are grouped together, the data that the l-th subcarrier needs to transmit is represented as:

[0081]

[0082] After SFC precoding, the orthogonal precoded codewords transmitted on the l-th subcarrier group are represented as:

[0083]

[0084] In this precoding matrix, the row dimension represents the subcarrier dimension, the column dimension represents the antenna dimension, the first row and the second row represent the codewords transmitted on the (2l+1)th and (2l+2)th subcarriers, respectively, and the first column and the second column represent the codewords transmitted on the first antenna and the second antenna, respectively.

[0085] definition Represents any one of the subcarriers in the l-th group (n 2l+1 ,n 2l+2 Because the subcarrier spacing used in the broadcast tower is relatively small, within any set of subcarriers, the base station f H Any subcarrier within a set of subcarriers and user k The channel parameters on the channel can be considered constant, i.e. Similarly, we can consider base station f H The power allocation is equal on any two adjacent subcarriers, that is... The broadcast service signal received by user k on the l-th subcarrier group is represented as:

[0086]

[0087] in, This indicates that user k is on subcarrier n. 2l+1and subcarrier n 2l+2 The additive white Gaussian noise introduced by the receiver has a mean of 0 and a variance of . The complex Gaussian random variable. From the receiving formula, it can be seen that the signal transmitted from the broadcast tower far from user k to user k is considered interference at user k because the cyclic prefix cannot cancel out the multipath delay. User k performs maximum ratio combining on the signals received on subcarrier group l:

[0088]

[0089]

[0090] To facilitate subsequent analysis of the system model, the following expression is defined:

[0091]

[0092] User k on subcarrier The signal-to-interference-plus-noise ratio (SIR) of the received signal can be written as:

[0093]

[0094] The first term in the denominator This indicates that the cyclic prefix of the signal transmitted by the base station from a distance of k cannot eliminate the multipath delay caused by the long distance on the subcarrier. The interference brought about by the above is represented as:

[0095]

[0096] The second term in the denominator represents the inter-carrier interference caused by the large Doppler frequency shift due to the high-speed movement of the terminal. The inter-carrier interference is converted into an interference term in the denominator using the statistical average of the ICI, and is expressed as:

[0097]

[0098] User k on subcarrier The rate at which broadcast services are received can be expressed as:

[0099]

[0100] Therefore, user k in BWP1 H The rate at which a frequency band receives broadcast services can be expressed as:

[0101]

[0102] From a systems perspective, BWP1 H The frequency band broadcast transmission rate can be used with access BWP1 HIt is represented by the minimum value of the broadcast service rate received by all users:

[0103]

[0104]

[0105] Similarly, we can conclude that The broadcast transmission rate of the carrier bandwidth portion can be expressed as:

[0106]

[0107]

[0108] (a.2) Cellular base station physical layer transmission model

[0109] Cellular base stations have relatively small coverage areas. When configuring 5G physical layer parameter sets, a longer subcarrier spacing and a shorter cyclic prefix are used. In the cellular base station network, cells are clustered within a specific range. All cellular base stations within the same cell cluster are grouped into a cooperative unit, and all cellular base stations in the same cell cluster collaboratively participate in the transmission of all user data within the cell cluster. The system requires three carrier bandwidth portions (BWP1) for each cellular base station. L , and They are respectively responsible for transmitting broadcast services for high-speed mobile users who are far from the broadcast tower within the cooperative cell, transmitting multicast services for all users within the system, and transmitting unicast services for all users within the system.

[0110] If the cooperating cell cluster is located near a macro base station, broadcast services from all users within the cooperative transmission area can be transmitted by the macro base station, and the cellular base station may not allocate the carrier bandwidth portion BWP1 for broadcast service transmission. L If the cooperating cell is far from the macro base station, the high-speed mobile user broadcast service within the cooperative transmission area is carried by the cellular base station, and the cellular base station needs to allocate part of the carrier bandwidth BWP1. L Without losing the generality of the analysis, this solution discusses scenarios where there are users in the collaborative area who need to receive broadcast services.

[0111] Let the number of cooperative cellular base stations be F. L The set of cellular base stations is represented as The user set is represented as The sets of users receiving broadcast, multicast, and unicast services are respectively denoted as follows: and The set of cellular base stations whose signals transmitted from a cellular base station to user k satisfy the distance allowed by the cyclic prefix of the transmitted signal is represented as follows: The number of antennas in a cellular base station is The user receiver uses a single antenna, and the cellular base station system bandwidth is B. L The subcarrier spacing is configured as Δf L The cellular base station frequency bands occupied by broadcast, multicast, and unicast services are β1B, respectively. L β2B L and β3B L The number of subcarriers used for transmitting broadcast, multicast, and unicast services are respectively and The sets of subcarriers for broadcast, multicast, and unicast services are respectively represented as follows: and Indicates cellular base station f L The channel parameters of user k on subcarrier n, Indicates cellular base station f L Channel parameters for user k on subcarrier n with the i-th antenna. Cellular base station f L The power for transmitting broadcast, multicast, and unicast is expressed as follows: and Indicates will Subcarriers On power, Indicates will Subcarriers On power, Indicates will Subcarriers The power on.

[0112] The transmission of cellular base station broadcast services adopts the Joint Transmission (JT) mode, where all base stations within the cell cluster share the channel state information and broadcast service data information of all users within the cooperative range, and jointly transmit broadcast services for users within the system. Multicast and unicast services adopt the Coordinated Schedule / Coordinated Beamforming (CS / CB) mode, where all cooperating base stations share the channel state information of all users, but do not share service data information, and joint precoding is performed on the cell cluster CDN server.

[0113] (a.2.1) Cellular Base Station Broadcast Service Transmission System Model

[0114] Because the number of receiving users for broadcast services is random, closed-loop precoding design cannot be based on channel state information fed back by specific users. Therefore, an open-loop MIMO precoding scheme is required. Cellular base stations have large subcarrier spacing at the physical layer and a short duration for an OFDM symbol in the time domain. Therefore, cellular base stations use Space-Time Block Code (STBC) for precoding design at the transmitting end. The flowchart for transmitting broadcast services in a cellular base station is shown below. Figure 9 As shown.

[0115] Literature analysis shows that only the number of antennas M... t The bitrate R will only be obtained when the value is 2. c The complex coding orthogonal matrix with a value of 1 has different maximum ratio combining formulas at the receiver for different STBC precoding matrices. To avoid sacrificing spectral efficiency due to precoding matrix design, the cellular base station uses the Alamouti space-time block code precoding scheme, and the number of transmitting antennas is... Two codewords are transmitted over two consecutive OFDM symbols in the time domain, with a code rate R. c =1. If the number of antennas at the cellular base station end... Then, the two most distant incoherent antennas in the antenna array are selected for STBC precoding transmission.

[0116] To ensure the correctness of the STBC precoding dimension without loss of generality, joint precoding analysis is considered over the time domain of two consecutive OFDM symbols. Let's assume that on the subcarrier... The data that a cellular base station needs to transmit in two consecutive time slots t1 and t2 is represented as follows:

[0117]

[0118] After STBC precoding, on the subcarrier The STBC precoding codewords on two consecutive time slots t1 and t2 can be represented as:

[0119]

[0120] In this precoding matrix, the row dimension represents the time-domain symbol dimension, the column dimension represents the antenna dimension, the first row and the second row represent the codewords transmitted on time-domain symbols t1 and t2, respectively, and the first column and the second column represent the codewords transmitted on the first antenna and the second antenna, respectively.

[0121] Because the physical layer subcarrier spacing of cellular base stations is relatively large, and the time domain of an OFDM symbol is short, the base station f can be considered as having a relatively short time domain of two consecutive symbol times t1 and t2. H The channel parameters of user k on subcarrier n remain unchanged, i.e. Similarly, we can assume that the power distribution of a cellular base station is the same over two consecutive symbol times t1 and t2, that is: Cellular base stations transmit broadcast services using Joint Transmission (JT) mode, where all cooperating cellular base stations use the same power allocation scheme to transmit broadcast services.

[0122] User k on subcarrier The broadcast service signals received within two consecutive time slots t1 and t2 are represented as follows:

[0123]

[0124] in, Indicates that user k is on a subcarrier The additive white Gaussian noise introduced by the receiver during two consecutive symbol times t1 and t2 has a mean of 0 and a variance of Δf. L Z0 is a complex Gaussian random variable. From the receiving formula, it can be seen that the signal transmitted from a cellular base station far from user k to user k is considered interference at user k because the cyclic prefix cannot cancel the multipath delay. User k corresponds to the subcarrier... The signals received within two consecutive symbol times t1 and t2 are combined using the maximum ratio.

[0125]

[0126]

[0127] To facilitate subsequent analysis of the system model, the following expression is defined:

[0128]

[0129] It is possible to obtain user k on the subcarrier The average signal-to-interference-plus-noise ratio (SIR) within two consecutive time slots t1 and t2 can be expressed as:

[0130]

[0131] The first term in the denominator This indicates that the cyclic prefix of the transmitted signal cannot eliminate the multipath delay caused by the long distance at a cellular base station located far from user k on the subcarrier. The interference signal introduced from above is represented as:

[0132]

[0133] The second term in the denominator represents the inter-carrier interference caused by the Doppler frequency shift due to the high-speed movement of the terminal. The inter-carrier interference is converted into an interference term in the denominator using the statistical average of the ICI, expressed as:

[0134]

[0135] User k on subcarrier The rate at which broadcast services are received can be expressed as:

[0136]

[0137] User k in BWP1 L The rate at which the carrier bandwidth receives broadcast services can be expressed as:

[0138]

[0139] From a systems perspective, BWP1 L The frequency band broadcast transmission rate can be used to access BWP1 L It is represented by the minimum value of the broadcast service rate received by all users:

[0140]

[0141]

[0142] (a.2.2) Cellular Base Station Multicast Service Transmission System Model

[0143] In this system, multicast service transmission involves bidirectional, feedback-based communication between the base station and the user. The CDN edge server within the cell cluster performs joint precoding design based on the channel state information fed back by the user. Let the cellular base station f... L In subcarrier The number of multicast service data carried on the upper layer is The multicast service carried is represented as:

[0144]

[0145] Among them, subcarrier The number of multicast services carried on the antenna cannot exceed the number of antennas, i.e. Each multicast service The precoding vector is represented as Then the cellular base station f L In subcarrier The precoding matrix for multicast services is represented as follows:

[0146]

[0147] Cellular base station f L In subcarrier Each multicast service The allocated power is Right now Then the cellular base station f L In subcarrier The power allocation matrix on can be written as:

[0148]

[0149] Then the cellular base station f L In subcarrier The signal sent from above can be represented as:

[0150]

[0151] For the transmission of multicast services, in order to analyze generality, we make the following assumptions.

[0152] 1. Let base station f L Users within the coverage area only receive signals from base station f L Multicast service data transmitted by adjacent cooperating cells on the same subcarrier is considered interference and should be eliminated using zero-breaking precoding.

[0153] 2. Assume that at base station f L Subcarriers within coverage area Each user receives only one type of multicast service data, and there is no situation where the same user is on the same subcarrier. The situation of receiving different multicast services.

[0154] 3. Assume that at base station f L Within the coverage area, each user receives multicast signals transmitted on a single subcarrier, and there is no situation where a user receives multicast services on multiple subcarriers.

[0155] Let cellular base station f L In subcarrier Multicast services The set of receiving users is represented as Cellular base station f L Employing a zero-forcing (ZF) precoding scheme ensures that the cellular base station f L In subcarrier Upload multicast services The precoding vector is located between all users who do not receive this multicast service and the cellular base station f. L The null space of the channel can be represented as:

[0156]

[0157] For users Because the base station transmitter uses a zero-breaking precoding design, it can only receive signals from cellular base station f. L In subcarrier Multicast services Received from base station f L In subcarrier Other multicast services on the carrier have zero power, and the received data is from neighboring cells on the subcarrier. The multicast service power on the carrier is zero, and at the same time, it receives signals from all base stations on the subcarrier. The multicast service power on the network is zero, which can be represented as:

[0158]

[0159]

[0160]

[0161]

[0162] Cellular base station f L Receiving multicast services within the coverage area users In subcarrier The received signal is represented as:

[0163]

[0164] The second term in the receiving formula represents the user. Received from base station f L In subcarrier Other multicast service information on the network, the third term of the receiving formula represents the user Received from neighboring base stations on subcarriers The interference information above, the fourth term represents the additive white Gaussian noise introduced by the receiver, satisfies

[0165] Because multicast services use zero-breaking precoding for transmission, users In subcarrier The power of other multicast services received is 0, that is... Then the inter-carrier interference caused by user k's high-speed movement also becomes 0, that is:

[0166]

[0167] Then the user Receiving multicast services The signal-to-interference-plus-noise ratio can be written as:

[0168]

[0169] Then the user Receiving multicast services The rate can be expressed as:

[0170]

[0171] From the perspective of system transmission, multicast services The transmission rate is expressed as the minimum rate at which users receive this multicast service, and is represented as:

[0172]

[0173] From the perspective of system transmission, base station f L In the carrier bandwidth section The transmission rate of multicast services can be expressed as:

[0174]

[0175]

[0176] (a.2.3) Cellular base station unicast service transmission system model

[0177] In this system, unicast service transmission involves bidirectional, one-to-one communication between the base station and the user, with feedback mechanisms. The CDN edge server within the cell cluster performs joint precoding design based on the channel state information fed back by the user. Let the cellular base station f... L In subcarrier The service user set is The number of unicast service data carried is The unicast service carried is represented as:

[0178]

[0179] The number of unicast services carried on each subcarrier cannot exceed the number of antennas, i.e. Transmitted to user Unicast service The precoding vector is represented as Then the cellular base station f L In subcarrier The precoding matrix for unicast services can be represented as:

[0180]

[0181] Cellular base station f L In subcarrier Each unicast service The allocated power is Right now Then the cellular base station f LIn subcarrier The power allocation matrix on can be written as:

[0182]

[0183] Then the cellular base station f L In subcarrier The transmitted signal can be represented as:

[0184]

[0185] For unicast service transmission, cellular base station f L Employing a zero-forcing (ZF) precoding scheme enables the use of subcarriers... Single-cast business The precoding vector is located in the unicast user set Excluding users All users who do not receive this unicast service to the cellular base station f L The null space can be represented as:

[0186]

[0187] For receiving unicast services users Because the base station transmitter uses a zero-breaking precoding design, user k can correctly receive unicast services. Received from base station f L In subcarrier Other unicast services on the carrier have zero power, and the received data is from neighboring cells on the subcarrier. The unicast service power on the subcarrier is zero, and at the same time, it receives signals from all base stations on the subcarrier. The unicast service power on the network is zero, which is represented as:

[0188]

[0189]

[0190]

[0191]

[0192] For cellular base station f L Receiving unicast services within the coverage area users In subcarrier The received signal can be represented as:

[0193]

[0194] The second term in the receiving formula represents the user. Received from base station f L In subcarrier Other unicast service information received; the third term in the formula represents the user. Received from neighboring base stations on subcarriers The interference unicast information above, the fourth term represents the additive white Gaussian noise due to the receiver, satisfies

[0195] Because unicast services use zero-breaking precoding for transmission, users In subcarrier The received unicast service power is 0, that is Then the inter-carrier interference caused by user k's high-speed movement also becomes 0, that is:

[0196]

[0197] Then the user In subcarrier Upload unicast service The signal-to-interference-plus-noise ratio can be written as:

[0198]

[0199] Then the user Receive unicast services The rate can be expressed as:

[0200]

[0201] The sum rate of unicast users within the system can then be expressed as:

[0202]

[0203]

[0204] b) Power Allocation Problem and Solution Analysis

[0205] Based on the proposed system model, this section allocates physical layer bandwidth and power resources for multi-service transmission in heterogeneous networks. The optimization objective is to maximize unicast transmission and rate within the system while ensuring the transmission rates of broadcast and multicast within the system.

[0206] (b.1) Resource allocation of the physical layer of the broadcast tower

[0207] From a system perspective, physical layer bandwidth and power resources are allocated to all users accessing the broadcast tower. The optimization objective is to maximize the minimum broadcast service transmission rate for all users accessing the broadcast tower. The optimization variables are bandwidth allocation factors α1 and α2 and the carrier bandwidth portion BWP1.H , Power allocated to each subcarrier The optimization problem can be written as:

[0208]

[0209] stα1+α2≤1

[0210]

[0211]

[0212]

[0213] The variables in this optimization problem include the power allocated on the subcarriers. And bandwidth allocation factors a1, a2, due to the uncertainty of the values ​​of variables α1, α2, frequency domain BWP1 H and Number of subcarriers and Things will change. and Since the number of variables is uncertain, the solution cannot be directly applied using the approach for convex optimization problems. To maximize the broadcast service transmission rate, the system bandwidth must be utilized as much as possible; the constraint α1+α2≤1 can be rewritten as α1+α2=1. This paper employs an algorithm based on a combination of genetic algorithm and convex optimization. The genetic algorithm is used to determine the number of subcarriers. and Iterative selection is performed using genetic algorithms for population selection, chromosome crossover, and chromosome mutation, within a fixed range. and Find the global optimal solution.

[0214] (b.2) Allocation of physical layer resources for cellular base stations

[0215] In a cooperative cellular base station cluster, the system optimization objective is to maximize the unicast and multicast transmission rates of the cellular network while ensuring the broadcast and multicast transmission rates of the cellular network.

[0216] (b.2.1) Honeycomb Analysis of Base Station Broadcast Service Optimization Issues

[0217] By optimizing the broadcast service transmission of the broadcast tower, the access broadcast tower BWP1 can be obtained. H and Minimum receive rate for all user broadcast services In cooperative cellular networks, the broadcast service transmission rate must not be less than [a certain value]. That is, it needs to meet the following:

[0218]

[0219]

[0220] To achieve the optimization goal of maximizing the unicast service transmission rate of cellular base stations, it is necessary to minimize the power allocated by the cellular base station to broadcast services while meeting the constraint of the broadcast service transmission rate required by the cellular base station. The optimization problem can be written as follows:

[0221]

[0222]

[0223]

[0224]

[0225]

[0226] For this optimization problem, there are two variables. And β1, since the bandwidth allocation factor β1 is uncertain, BWP1 L Number of subcarriers uncertain, The number of variables is uncertain, making it impossible to directly solve the optimization problem.

[0227] Considering the actual carrier bandwidth portion BWP1 L The deployment and optimization problem are solved using a step-by-step method, and the algorithm flowchart is shown in the table below. First, under the condition of power equalization of the cooperative cellular base stations, and by applying the constraint that the transmission rate of broadcast services in the cellular network is not less than the minimum transmission rate of broadcast services obtained from the broadcast tower, the minimum number of subcarriers required for the cellular network to transmit broadcast services is calculated through subcarrier iteration. And set The number of subcarriers required for actual broadcast service transmission is then used in the optimization problem. It is a constant, only A single variable can be used to solve convex optimization problems.

[0228]

[0229] (b.2.2) Analysis of Optimization Issues for Multicast Services in Cellular Base Stations

[0230] Let the multicast service transmission rate threshold set within the system be... Within the cooperative cell cluster, each base station's multicast service transmission rate must meet a condition greater than or equal to the multicast transmission threshold, i.e.:

[0231]

[0232]

[0233] To achieve the optimization goal of maximizing unicast service transmission rate in cellular base stations, it is necessary to minimize the cellular base station's f_transmission rate while satisfying the constraint of the multicast service transmission rate required by the cellular base station. L Power allocated to multicast services The optimization problem can be written as follows:

[0234]

[0235]

[0236]

[0237]

[0238]

[0239]

[0240] For this optimization problem, there are two variables. And β2, since the bandwidth allocation factor β2 is uncertain, Number of subcarriers uncertain, The number of variables is uncertain, making it impossible to directly solve the optimization problem.

[0241] Considering the actual carrier bandwidth portion The deployment and optimization problem is solved using a step-by-step method, and the algorithm flowchart is shown in the table below. First, under the condition of power equalization of the cooperating cellular base stations, and by constraining that the transmission rate of multicast services in the cellular network is not less than the set multicast service transmission threshold of the cellular base stations, the minimum number of subcarriers required for multicast service transmission in the cellular network is calculated through subcarrier iteration. and set The number of subcarriers required for actual multicast service transmission is then used in the optimization problem. It is a constant, only A single variable can be used to solve convex optimization problems.

[0242]

[0243]

[0244] (b.2.3) Analysis of unicast service optimization issues in cellular base stations

[0245] Cellular base station f LIn addition to transmitting broadcast and multicast services, using To maximize unicast speed and rate within the system, using multiple subcarriers to transmit unicast services, the following optimization problem can be constructed:

[0246]

[0247]

[0248]

[0249]

[0250] In summary, this invention proposes a system logical architecture for joint multi-antenna transmission between broadcast towers and cellular base stations under a CU and DU separation mode. This architecture enables the joint transmission of broadcast, multicast, and unicast services by broadcast towers and cellular base stations within a unified CDN network deployment. Furthermore, the design of a CU and DU separation mode at both the broadcast tower and cellular base station ends improves the efficiency of signaling transmission at the base station. Additionally, the algorithm for joint transmission between broadcast towers and cellular base stations in this invention has been implemented and its specific functional modules have been found in actual network deployments.

[0251] This invention proposes a transmission mode design for broadcast, multicast, and unicast services in scenarios where both broadcast towers and cellular base stations have multiple antennas, thereby improving the system's channel capacity by using multiple antennas.

[0252] This invention designs different precoding schemes for the different transmission characteristics of broadcast, multicast, and unicast services. In the broadcast service transmission of broadcast towers, the Space Frequency Code (SFC) precoding scheme is used. In the broadcast service carrier bandwidth of cellular base stations, the Space Time Block Code (STBC) precoding scheme is used. In the multicast service carrier bandwidth of cellular base stations, the Zero-Forcing (ZF) precoding scheme is adopted. In the unicast service carrier bandwidth, the Zero Forcing (ZF) precoding scheme is used.

[0253] This invention, based on the transmission mode where both broadcast towers and cellular base stations have multiple antennas, performs joint resource allocation of physical layer bandwidth and power within the system. The optimization objective is to maximize the transmission and rate of unicast within the system while ensuring the transmission rates of broadcast and multicast within the system.

[0254] Through the description of specific embodiments, a more in-depth and specific understanding should be gained of the technical means and effects adopted by the present invention to achieve the intended purpose. However, the accompanying drawings are only provided for reference and illustration and are not intended to limit the present invention.

Claims

1. A heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation, characterized in that, The transmission architecture separates the CU and DU at the base station end. The transmission architecture includes a broadcast tower network and a cellular network with heterogeneous networks. Both the broadcast tower network and the cellular network are deployed with multi-antenna transmission. The data transmitted by the broadcast tower network and the cellular network are distributed through a CDN network to jointly transmit broadcast, multicast and unicast services. The CDN server transmits the channel status information of the broadcast tower fed back by the user to the CU, performs space frequency code precoding at the CU, and transmits the encoded information to the RRU via the DU and sends it to the user. A CU-MC module is added at the base station parallel to the CU to process multicast and broadcast user data. At the CU-MC module, the user broadcast service information that needs to be carried by the cellular network is precoded using space-time block codes. At the CU, ZF precoding of user unicast information and ZF precoding of multicast information are performed. At the receiving end, users select different carrier bandwidth portions of the broadcast tower and cellular base station based on their location and movement speed. After channel estimation, the channel information is fed back to the cellular base station through the FDD channel, and then unified resource allocation is performed through the CDN server.

2. The heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation according to claim 1, characterized in that, The cellular base station of the cellular network is divided into three carrier bandwidth portions, which are respectively used to transmit broadcast services for mobile users within the system who are more than a preset distance from the broadcast tower, to transmit multicast services for all users within the system, and to transmit unicast services for all users within the system.

3. The heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation according to claim 2, characterized in that, In the broadcast service carrier bandwidth portion of the cellular base station, space-time block coding is used for precoding; in the multicast service carrier bandwidth portion of the cellular base station, zero-breaking precoding is used; and in the unicast service carrier bandwidth portion of the cellular base station, zero-breaking precoding is used.

4. The heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation according to claim 1, characterized in that, In a cellular base station system, cells are clustered within a preset range. All cellular base stations within the same cell cluster are classified as a cooperative unit. Transmission points located in the same cooperative unit cooperate to send or receive user data within the corresponding cooperative unit.

5. The heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation according to claim 4, characterized in that, For cell clusters where broadcast services are carried by cellular cells, open-loop MIMO precoding is used for precoding.

6. The heterogeneous network joint multi-antenna transmission architecture based on CU and DU separation according to claim 1, characterized in that, The transmission architecture feeds back the channel information of the broadcast tower and cellular base station selected by the user through the FDD channel to the cellular base station, and performs unified resource allocation through the CDN server.

Images