Frequency reuse implementation method of ground-air broadband communication system

Abstract

The invention discloses a frequency multiplexing implementation method of a ground-air broadband communication system, which comprises the following steps: setting a plurality of multiplexing frequencies for aggregating downlink subcarriers for the ground-air broadband communication system, the plurality of multiplexing frequencies multiplexing the frequency of a ground operator system; arranging a ground-air system base station which is spatially isolated from a ground same-frequency network base station of the ground operator system for the ground-air broadband communication system along an air route according to the plurality of multiplexing frequencies; according to the coverage condition of a plurality of multiplexing frequencies in the ground operator system, selecting an actual multiplexing frequency for the laid ground-air system base station from the plurality of multiplexing frequencies; and realizing ground-to-air communication of the ground-to-air broadband communication system by using the actual multiplexing frequency of the ground-to-air system base station. According to the frequency multiplexing technology, the inter-system co-frequency interference caused by frequency multiplexing can be reduced, and the design complexity and the construction cost are low.

Description

Technical Field

[0001] The present invention relates to the fields of aviation and communication technology, and in particular to a frequency reuse technology for a ground-to-air broadband communication system. Background Art

[0002] The ground-to-air broadband communication system refers to the deployment of ground base stations along the flight route, equipped with high-gain antennas to transmit wireless signals to the air, forming a ground-to-air communication link. Airborne terminals are deployed on the aircraft to receive ground signals and convert them into WLAN signals in the cabin, providing Internet access services for the terminals in the cabin.

[0003] In response to the special needs of Doppler frequency shift and ultra-long-distance coverage (single base station coverage radius > 300km) caused by the high-speed movement of civil aircraft, the ground-to-air broadband communication system has innovatively proposed targeted solutions. Compared with other technologies such as satellites, the ground-to-air communication system has obvious advantages in peak rate, user capacity, equipment, operation and maintenance costs, and is an extension of the ground cellular mobile communication system to aviation coverage.

[0004] With the rapid development of wireless communication technology, wireless frequency resources are currently in short supply. It is difficult to find enough spectrum resources dedicated to ground-to-air broadband communication networks. Only spectrum resources with smaller bandwidths can be found, which cannot meet the business needs of ground-to-air broadband communication networks. To this end, the network bandwidth of the ground-to-air broadband communication system can generally be increased by reusing the frequency resources of other ground systems, but the problem of co-frequency interference caused by this needs to be solved. The conventional method is to reuse the same frequency band for the entire network and reduce interference by adopting a series of means such as parameter design, power control, customized antennas, and spatial isolation. However, the design of this method is complex and difficult, and the design and construction costs are high. Summary of the invention

[0005] The present invention provides a method for realizing frequency reuse of a ground-to-air broadband communication system, aiming to solve the problems of co-frequency interference caused by the ground-to-air broadband communication system reusing frequency resources of other ground systems, as well as the high design complexity and construction cost.

[0006] The present invention provides a method for realizing frequency reuse in a ground-to-air broadband communication system, the method comprising: setting an uplink dedicated frequency and a downlink dedicated frequency, and a plurality of reused frequencies used as aggregated downlink subcarriers for the ground-to-air broadband communication system, wherein the plurality of reused frequencies reuse the frequency of a ground operator system; according to the ground-to-air broadband communication system and the plurality of reused frequencies of the ground operator system, deploying a ground-to-air system base station that is spatially isolated from a ground same-frequency network base station of the ground operator system along an air route for the ground-to-air broadband communication system; according to the coverage of the plurality of reused frequencies in the ground operator system, selecting an actual reused frequency for the deployed ground-to-air system base station from the plurality of reused frequencies; utilizing the uplink dedicated frequency to perform air-to-ground communication of the ground-to-air broadband communication system, and utilizing the downlink dedicated frequency and the actual reused frequency of the ground-to-air system base station to perform ground-to-air communication of the ground-to-air broadband communication system.

[0007] Preferably, according to the multiple reused frequencies of the ground-to-air broadband communication system and the ground operator system, the ground-to-air system base station spatially isolated from the ground co-frequency network base station of the ground operator system is deployed along the route for the ground-to-air broadband communication system, including: for any reused frequency of the ground-to-air broadband communication system and the ground operator system, determining the spatial isolation distance between the ground-to-air system base station of the ground-to-air broadband communication system and the ground co-frequency network base station of the ground operator system based on the reused frequency; and according to the spatial isolation distance, the ground-to-air system base station spatially isolated from the ground co-frequency network base station of the ground-to-air broadband communication system is deployed along the route for the ground-to-air broadband communication system.

[0008] Preferably, selecting an actual multiplexing frequency from multiple multiplexing frequencies for the deployed ground-to-air system base station according to the coverage of multiple multiplexing frequencies in the ground operator system includes: obtaining the coverage of each of the multiple multiplexing frequencies of the ground operator system; dividing into multiple areas according to the coverage of each of the multiple multiplexing frequencies of the ground operator system, wherein the coverage range of the multiple multiplexing frequencies of the ground operator system in each area is different; for any area, finding the multiplexing frequency from the multiple multiplexing frequencies that minimizes the coverage range of the ground operator system in the area, and using the found multiplexing frequency as the actual multiplexing frequency of the ground-to-air system base station deployed in the area.

[0009] Preferably, the method also includes: installing an airborne terminal having an airborne dedicated frequency transceiver module and an airborne multiplexed frequency receiving module on the aircraft, and configuring the actual multiplexed frequency for the airborne multiplexed frequency receiving module to receive the signal transmitted by the ground-to-air system base station using the actual multiplexed frequency; installing an omnidirectional antenna connected to the airborne dedicated frequency transceiver module as an airborne dedicated frequency RF antenna and installing a phased array antenna connected to the airborne multiplexed frequency receiving module as an airborne multiplexed frequency RF antenna on the aircraft; configuring an RRU and a directional antenna for the ground-to-air system base station as a base station dedicated frequency RF module and configuring an AAU as a base station multiplexed frequency transmitting module, and configuring the actual multiplexed frequency for the base station multiplexed frequency transmitting module to transmit signals to the airborne terminal using the actual multiplexed frequency.

[0010] Preferably, the method also includes: setting a data storage unit in the airborne terminal, and pre-storing basic information of all ground-to-air system base stations of the ground-to-air broadband communication system in the data storage module, wherein the basic information includes site name, base station ID, cell name, cell ID, cell PCI, location information, and supported frequency bands.

[0011] Preferably, before using the uplink dedicated frequency to carry out air-to-ground communication of the ground-to-air broadband communication system and using the downlink dedicated frequency and the actual reused frequency of the ground-to-air system base station to realize ground-to-air communication of the ground-to-air broadband communication system, the method also includes: the airborne terminal randomly accesses the cell of the ground-to-air broadband communication system by executing an initial network access process to obtain the reused frequency, or the airborne terminal obtains the reused frequency by executing an inter-cell switching process; the airborne terminal synchronously modifies the actual reused frequency of its airborne reused frequency receiving module according to the reused frequency, and determines the actual service cell by executing a service cell confirmation process; the airborne terminal controls its airborne reused frequency radio frequency antenna to point the beam to the actual service cell to realize ground-to-air communication between the airborne terminal and the actual service cell.

[0012] Preferably, the airborne terminal randomly accesses a cell of the ground-to-air broadband communication system by executing an initial network access process to obtain a reused frequency, including: the airborne terminal performs a cell search on a downlink dedicated frequency to randomly access the searched and selected cell; the airborne terminal receives an RRC reconfiguration message of the randomly accessed cell, and obtains the reused frequency from the RRC reconfiguration message.

[0013] Preferably, the airborne terminal obtains the reused frequency by executing the inter-cell switching process, including: the airborne terminal performs co-frequency measurement, measures the signals of the surrounding dedicated frequencies and reports a measurement report; the airborne terminal receives an RRC reconfiguration message sent by the current cell after making an inter-cell switching decision based on the measurement report, and obtains the target cell information to be switched from the RRC reconfiguration message, the target cell information includes the reused frequency of the target cell; the airborne terminal performs random access to the target cell on the downlink dedicated frequency.

[0014] Preferably, the airborne terminal determines the actual service cell by executing an inter-cell switching process, including: the airborne terminal obtains the PCI information of the randomly accessed cell, filters out cells using the same PCI from the pre-stored basic information of all ground-to-air system base stations, and generates a list of candidate service cells; the airborne terminal calculates the distance between the airborne terminal and each candidate service cell according to the current position information obtained in real time by the GPS receiver during the movement of the aircraft and the position information of each candidate service cell in the candidate service cell list; the airborne terminal confirms the candidate service cell corresponding to the shortest distance as the actual service cell of the airborne terminal.

[0015] Preferably, the airborne terminal controls its airborne multiplexed frequency radio frequency antenna to direct the beam toward the actual service cell, including: the airborne terminal determines the relative angle between the current position of the aircraft and the position of the actual service cell based on the current position information acquired in real time by a GPS receiver during the movement of the aircraft and the position information of the actual service cell; the airborne terminal controls the airborne multiplexed frequency radio frequency antenna to direct the beam toward the actual service cell based on the relative angle between the current position of the aircraft and the position of the actual service cell.

[0016] The present invention provides a method for realizing frequency reuse of a ground-to-air broadband communication system. In the case of limited frequency resources, the frequency resources of multiple frequency bands jointly built and shared by ground operators are reasonably reused to improve the spectrum utilization rate and increase the transmission bandwidth of the ground-to-air communication network. In addition, by reasonably setting the spatial isolation of the same-frequency base stations between systems, using the reused frequency only for downlink (i.e., ground-to-air) one-way data transmission, and flexibly using different reused frequencies in different areas, the same-frequency interference between systems caused by frequency reuse is reduced, while reducing the complexity of solution design and construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of a method for realizing frequency reuse of a ground-to-air broadband communication system provided by the present invention;

[0018] Figure 2It is a schematic diagram of interference types in a scenario where a ground-to-air system base station and a ground co-frequency network base station coexist in a ground-to-air broadband communication system provided by the present invention;

[0019] Figure 3 It is an architecture diagram of the ground-to-air broadband communication system provided by the present invention;

[0020] Figure 4 This is a diagram of the parameters related to the TDD time slot configuration of the conventional 5G NR system;

[0021] Figure 5 It is a schematic diagram of the time slot configuration of the multiplexing frequency band of the conventional 5G NR system and the ground-to-air broadband communication system of the present invention under the TDD standard;

[0022] Figure 6a and Figure 6b It is a schematic diagram of the design frequency scheme of the ground-to-air broadband communication system of the present invention;

[0023] Figure 7 It is a simulation calculation diagram of the spatial isolation between the 3.5GHz frequency band base station of the ground-to-air broadband communication system of the present invention and the ground co-frequency network base station;

[0024] Figure 8 It is a schematic diagram of the division of the coverage area of ​​the ground F3 and F4 frequency networks designed by the present invention;

[0025] Fig. 9 It is a schematic diagram of the ground-to-air broadband communication system of the present invention coexisting with the ground F3 / F4 frequency network;

[0026] Fig.10 It is a schematic diagram of the process of initial network access of the airborne terminal of the present invention;

[0027] Fig.11 It is a schematic diagram of the process of switching between cells of the airborne terminal of the present invention;

[0028] Fig.12 It is a schematic diagram of the process of the airborne terminal determining the actual serving cell of the present invention. DETAILED DESCRIPTION

[0029] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0030] The present invention provides a frequency reuse implementation method for a ground-to-air broadband communication system, which adopts a frequency scheme of "dedicated small bandwidth frequency (hereinafter referred to as dedicated frequency) + multiple reused large bandwidth frequencies (hereinafter referred to as reused frequency)". The dedicated frequency ensures network coverage, and the reused frequency improves the network bandwidth of the ground-to-air broadband communication system, providing more passengers with diversified data business services to meet user experience. At the same time, it can dynamically adjust which reused frequency is actually used among multiple reused frequencies, and reduce the same-frequency interference between systems through technical means such as spatial isolation and downlink unidirectional data transmission, reduce the impact on the ground same-frequency network, improve spectrum utilization, and reduce system design complexity and construction costs.

[0031] See also Figure 1 The method for realizing frequency reuse of the ground-to-air broadband communication system provided by the present invention comprises the following steps:

[0032] Step S101: setting an uplink dedicated frequency and a downlink dedicated frequency for the ground-to-air broadband communication system, and multiple multiplexed frequencies used as aggregated downlink subcarriers, wherein the multiple multiplexed frequencies multiplex the frequencies of the ground operator system.

[0033] The frequency scheme of the ground-to-air broadband communication system of the present invention is "dedicated frequency + multiple multiplexed frequencies".

[0034] Among them, the ground-to-air broadband communication system adopts mature 5G NR communication technology, with dedicated frequencies as the main carrier, including uplink frequency F1 and downlink frequency F2, which are responsible for signaling interactions such as cell selection, initial access, and inter-cell switching of airborne terminals and uplink and downlink data transmission.

[0035] Among them, the reused frequency can select the large bandwidth frequency resources jointly built and shared by the ground operator system (or other ground systems), which are sufficient, such as the ground communication operator frequency, the vehicle network frequency, etc., and at least include 2 reused frequencies, such as reused frequency F3 and reused frequency F4, and the reused frequencies actually used can be flexibly configured according to the conditions. The reused frequency is used as a subcarrier only for downlink, that is, the reused frequency is used as an aggregated downlink subcarrier mainly for downlink data transmission.

[0036] Step S102: According to the multiple reused frequencies of the ground-to-air broadband communication system and the ground operator system, a ground-to-air system base station spatially isolated from the ground co-frequency network base station of the ground operator system is deployed along the route for the ground-to-air broadband communication system.

[0037] A sufficient / reasonable spatial distance / interval should be maintained between the ground-to-air system base station of the ground-to-air broadband communication system and the ground co-frequency network base station of other ground systems (hereinafter referred to as the ground co-frequency base station) so as not to affect the ground co-frequency network. Therefore, for any reused frequency of the ground-to-air broadband communication system and the ground operator system, firstly, based on the reused frequency, the spatial isolation distance between the ground-to-air system base station of the ground-to-air broadband communication system and the ground co-frequency network base station of the ground operator system is determined, and then, according to the spatial isolation distance, the ground-to-air system base station that is spatially isolated from the ground co-frequency network base station of the ground-to-air broadband communication system is arranged along the route for the ground-to-air broadband communication system. For example, if the 3.5GHz frequency of the ground communication operator is to be reused, through simulation calculation, when the minimum isolation distance is 5 kilometers, the requirement that the ground NR network noise floor is less than 2db can be met. Therefore, when the ground-to-air system base station of the ground-to-air broadband communication system is arranged, the spacing distance between the ground co-frequency base station of the ground communication operator using the 3.5GHz frequency should be greater than 5 kilometers.

[0038] Step S103: According to the coverage of multiple reuse frequencies in the ground operator system, select an actual reuse frequency for the deployed ground-to-air system base station from multiple reuse frequencies.

[0039] In order to further reduce the inter-system co-frequency interference caused by frequency reuse to the ground co-frequency network, the ground-to-air broadband communication system of the present invention flexibly uses different reused frequencies in different areas. Specifically, the coverage of each of the multiple reused frequencies of the ground operator system is obtained, and multiple areas are divided according to the coverage of each of the multiple reused frequencies of the ground operator system. The coverage range of the multiple reused frequencies of the ground operator system in each area is different. For any area, the reused frequency that minimizes the coverage range of the ground operator system in the area is found from the multiple reused frequencies, and the found reused frequency is used as the actual reuse frequency of the ground-to-air system base station deployed in the area. Assume that the ground-to-air broadband communication system reuses the three frequencies (F1, F2, F3) of the ground operator system, and divides it into three areas according to the coverage of the three frequencies of the ground operator system. The F1 frequency coverage of the ground operator system in area 1 is less than the F2 frequency coverage and the F3 frequency coverage. The F2 frequency coverage of the ground operator system in area 2 is less than the F1 frequency coverage and the F3 frequency coverage. The F3 frequency coverage of the ground operator system in area 3 is less than the F1 frequency coverage and the F2 frequency coverage. Then, the ground-to-air broadband communication system can use F1 as the actual multiplexing frequency in area 1, use F2 as the actual multiplexing frequency in area 2, and use F3 as the actual multiplexing frequency in area 3.

[0040] Step S104: using the uplink dedicated frequency to perform air-to-ground communication of the ground-to-air broadband communication system, and using the downlink dedicated frequency and the actual reuse frequency of the ground-to-air system base station to perform ground-to-air communication of the ground-to-air broadband communication system.

[0041] To realize the ground-to-air broadband communication system, it is necessary to install a ground-to-air communication airborne terminal (hereinafter referred to as the airborne terminal) on the aircraft, install a multiplexed frequency and dedicated frequency radio frequency antenna on the outer surface of the aircraft, and deploy multiple ground-to-air system base stations along the aircraft route.

[0042] Among them, the airborne terminal has an airborne dedicated frequency transceiver module and an airborne multiplexed frequency receiving module, and the airborne multiplexed frequency receiving module can flexibly configure the actual multiplexed frequency (or the actual used frequency) to receive the signal transmitted by the ground-to-air system base station using the actual multiplexed frequency. In addition, a data storage unit can also be provided in the airborne terminal, and the basic information of all ground-to-air system base stations of the ground-to-air broadband communication system is pre-stored in the data storage module. The basic information of each ground-to-air system base station may include site name, base station ID, cell name, cell ID, cell PCI, location information (longitude, latitude, altitude), supported frequency band (uplink dedicated frequency / downlink dedicated frequency + actual multiplexed frequency among multiple multiplexed frequencies), and may also include the province to which it belongs, the city to which it belongs, etc.

[0043] Among them, the above-mentioned multiple RF antennas of the aircraft are connected to the airborne terminal through interconnection cables. Specifically, the airborne multiplexed frequency RF antenna installed on the outer surface of the aircraft adopts a phased array antenna, which supports a wide frequency (supports the selected multiplexed frequency). It receives the multiplexed frequency band signal through a directional beam, reduces the reception of the same-frequency interference signal on the ground, and is connected to the airborne multiplexed frequency receiving module to transmit the received multiplexed frequency band signal to the airborne multiplexed frequency receiving module; the airborne special frequency RF antenna installed on the outer surface of the aircraft adopts an omnidirectional antenna for aviation purposes, which is connected to the airborne special frequency transceiver module.

[0044] Among them, each ground-to-air system base station is equipped with a base station dedicated frequency RF module (or base station dedicated frequency transceiver module) and a base station reused frequency RF module (or base station reused frequency transmitting module). The base station dedicated frequency RF module can use RRU+ customized directional antenna, and the base station reused frequency transmitting module uses AAU. AAU uses broadband equipment, supports the selected reused frequency, and transmits directional transmission through beamforming to reduce interference with the ground co-frequency network. The actual reused frequency (or actual use frequency) can be flexibly set to use the actual reused frequency to transmit signals to the airborne terminal.

[0045] If a reused frequency in the ground operator system is the TDD standard (that is, the ground co-frequency network is the TDD standard), then when the ground-to-air broadband communication system reuses the frequency, the associated parameters such as the subcarrier spacing (SCS), uplink and downlink conversion period, uplink and downlink time slot ratio and subframe configuration are consistent with the ground co-frequency network configuration, and the ground-to-air broadband communication system only uses the downlink subframes (downlink data subframes), and does not use the uplink subframes (uplink data subframes) and flexible subframes; if a reused frequency in the ground operator system is the FDD standard (that is, the ground co-frequency network is the FDD standard), then the ground-to-air broadband communication system only uses the downlink frequency.

[0046] The airborne terminal can obtain the reused frequency in two ways. First, the airborne terminal randomly accesses the cell of the ground-to-air broadband communication system by executing the initial network access process to obtain the reused frequency. Specifically, the airborne terminal performs a cell search on the downlink dedicated frequency to randomly access the searched and selected cell, and then receives the RRC reconfiguration message of the randomly accessed cell, and obtains the reused frequency from the RRC reconfiguration message. Second, the airborne terminal obtains the reused frequency by executing an inter-cell switching process. Specifically, after the airborne terminal performs co-frequency measurement, measures the signals of the surrounding dedicated frequencies and reports the measurement report, it receives the RRC reconfiguration message issued by the current cell after making an inter-cell switching decision based on the measurement report, and obtains the target cell information to be switched from the RRC reconfiguration message, and the target cell information includes the reused frequency of the target cell.

[0047] After acquiring the reused frequency, the airborne terminal synchronously modifies the actual reused frequency of its airborne reused frequency receiving module according to the reused frequency, and determines the actual service cell by executing the service cell confirmation process, wherein the airborne terminal determines the actual service cell by executing the inter-cell switching process, which may include: the airborne terminal obtains the PCI information of the randomly accessed cell, filters out the cells using the same PCI from the basic information of all pre-stored ground-to-air system base stations, generates a list of candidate service cells, and calculates the distance between the airborne terminal and each candidate service cell according to the current position information obtained in real time by the GPS receiver during the movement of the aircraft and the position information of each candidate service cell in the candidate service cell list, so as to confirm the candidate service cell corresponding to the shortest distance as the actual service cell of the airborne terminal.

[0048] After determining the actual service cell, the airborne terminal controls its airborne multiplexing frequency radio frequency antenna to direct the beam toward the actual service cell, so as to realize ground-to-air communication between the airborne terminal and the actual service cell. Specifically, the airborne terminal determines the relative angle between the current position of the aircraft and the position of the actual service cell based on the current position information obtained in real time by the GPS receiver during the movement of the aircraft and the position information of the actual service cell, and controls the airborne multiplexing frequency radio frequency antenna to direct the beam toward the actual service cell based on the relative angle.

[0049] The frequency reuse technology of the present invention can improve spectrum utilization and increase the transmission bandwidth of the ground-to-air communication network by reasonably reusing frequency resources when frequency resources are limited, thereby providing a better ground-to-air broadband network for the majority of terminal passengers and satisfying user experience. It can also reduce the co-frequency interference between systems caused by frequency reuse, and has low design complexity and construction cost.

[0050] The following takes two multiplexing frequencies as an example, combined with Figures 2 to 12 Provide detailed explanation.

[0051] See also Figure 2 In the scenario where the ground-to-air system base stations used in the ground-to-air broadband communication system coexist with the ground co-frequency network base stations used by the ground operator system, frequency reuse will bring about the problem of co-frequency interference between systems, including interference of the ground-to-air system base stations on the ground terminals of the ground operator system and interference of the ground co-frequency network base stations on the airborne terminals.

[0052] See also Figure 3 The network architecture of the ground-to-air broadband communication system shown includes ground-to-air system base stations deployed along the aircraft route and airborne terminals installed on the aircraft. The frequency usage scheme of the ground-to-air broadband communication system is "dedicated frequency + multiple reused frequencies", where the dedicated frequency includes uplink and downlink frequencies (uplink is F1, downlink is F2), but bandwidth resources are limited, and the reused frequency can select frequency resources jointly built and shared by ground operators. It has sufficient spectrum resources, has 2 reused frequencies F3 and F4, and can flexibly configure one of the reused frequencies F3 and F4 as the actual use frequency according to conditions.

[0053] See also Figure 4 The relevant parameters of the conventional 5G NR system TDD time slot configuration and Figure 5The conventional 5G NR system TDD conventional subframe configuration schematic diagram and the ground-to-air system subframe configuration schematic diagram of the ground-to-air broadband communication system reuse frequency (TDD) of the present invention are shown. The ground reuse frequency band network (i.e., the ground same-frequency network) adopts the TDD method, and both uplink and downlink data transmission are carried out. In order to reduce interference between systems and reduce the complexity of system design, the ground-to-air broadband communication network reuse frequency of the present invention is only used for downlink data transmission, using downlink subframes, and uplink subframes and flexible subframes are not used.

[0054] See also Figure 6a , Figure 6b The frequency scheme of the ground-to-air broadband communication system shown in the figure is the scheme of using F3 and F42 multiplexing frequencies in the ground-to-air broadband communication network. Figure 6a The air-to-ground transmission uses F1 (dedicated frequency uplink), the ground-to-air transmission uses F2 (dedicated frequency downlink) and the downlink aggregation uses F3 (multiplexed frequency 1). Figure 6b The air-to-ground frequency F1 (dedicated uplink frequency) is used, and the ground-to-air frequency F2 (dedicated downlink frequency) is used. Downlink aggregation F4 (multiplexed frequency 2) is used. The present invention can flexibly select the frequency F3 and F4 based on the coverage of the ground frequency network. Figure 6a , Figure 6b Two frequency utilization schemes reduce the interference caused by co-frequency reuse.

[0055] See also Figure 7 The distance isolation requirements between the ground-to-air system base station of the ground-to-air broadband communication network and the operator's 3.5GHz ground co-frequency network base station are shown in the figure. After simulation calculation, the isolation between the ground-to-air system base station of the ground-to-air broadband communication network and the co-frequency 3.5GHz frequency base station is greater than 5 kilometers, which can meet the requirement that the ground co-frequency network noise floor rise is less than 2db.

[0056] There are two reuse frequencies used in the ground-to-air broadband communication system, namely F3 and F4. To analyze the network coverage of the ground F3 and F4 frequencies, refer to Figure 8 and Fig. 9 The network coverage distribution design of the ground operator system F3 and F4 frequencies (hereinafter referred to as ground F3 and F4 frequencies) and the schematic diagram of the coexistence of the ground-to-air broadband communication system and the ground F3 and F4 same-frequency network are shown. The actual reuse frequency of the ground-to-air system base station in the ground-to-air broadband communication system can be determined by the following steps:

[0057] Step 1.1: Obtain the usage of the ground F3 and F4 frequency networks, and divide them into two areas according to the coverage: Area ① is an area with more F3 frequency coverage and less F4 frequency coverage, and Area ② is an area with less F3 frequency coverage and more F4 frequency coverage.

[0058] Considering the large coverage range of the base stations of the ground-to-air broadband system, it is basically impossible for an area to have a large coverage of both F3 and F4 frequencies. If this occurs, interference can be avoided by introducing new reused frequencies.

[0059] Step 1.2: According to the above-mentioned ground network F3 and F4 frequency usage area division, the ground-to-air broadband base station in area ① uses the F4 frequency as the reuse frequency, and the ground-to-air broadband base station in area ② uses the F3 frequency as the reuse frequency.

[0060] When the airborne terminal of the present invention initially accesses the network or switches cells, the RRC reconfiguration message will carry downlink F3 or F4 frequency subcarrier information, and the airborne terminal configures the receiving module to receive the frequency of F3 or F4 according to this message. Random access and inter-cell switching are involved. The random access is a very critical step in the mobile communication system, which refers to the process from the airborne terminal sending a random access preamble to try to access the network to establishing a basic signaling connection with the network. The inter-cell switching refers to the process in which the airborne terminal moves from the coverage of one cell to the coverage of another cell during movement, and switches to another cell to provide service due to the poor signal of the original service cell.

[0061] See also Fig.10 The process of the airborne terminal initially accessing the network (referred to as accessing the network) includes the following steps:

[0062] Step 2.1: The airborne terminal searches for the dedicated frequency signal through the standard cell search process and selects the cell with the strongest signal, completes downlink synchronization, and demodulates the PCI and system messages.

[0063] Step 2.2: According to the system message, the airborne terminal performs a random access procedure in the selected cell and completes uplink synchronization.

[0064] Step 2.3: The airborne terminal receives the RRC reconfiguration message of the accessed cell and obtains the downlink subcarrier information, that is, the F3 or F4 frequency.

[0065] Step 2.4: The airborne terminal adjusts the frequency of the reused frequency band receiving module to the frequency in the RRC reconfiguration message, that is, the F3 or F4 frequency.

[0066] Step 2.5: The airborne terminal executes the service cell confirmation process and communicates normally with the ground base station.

[0067] See also Fig.11 The process of handover of the airborne terminal between different cells includes the following steps:

[0068] Step 3.1: Periodically or event-triggered, the airborne terminal performs co-frequency measurement, measures the signals of the surrounding dedicated frequencies and submits a measurement report.

[0069] Step 3.2: The source cell makes a handover decision based on the measurement report and notifies the airborne terminal of the target cell information to be handed over, including the downlink subcarrier information of the target cell, ie, the F3 or F4 frequency, through an RRC reconfiguration message.

[0070] Step 3.3: In the target cell, the airborne terminal performs a random access procedure on the dedicated frequency to complete uplink and downlink synchronization.

[0071] Step 3.4: The airborne terminal adjusts the frequency of the multiplexing frequency band receiving module to make it consistent with the configuration in the RRC reconfiguration message of the target cell, that is, the F3 or F4 frequency.

[0072] Step 3.5: The terminal executes the service cell confirmation process and communicates normally with the ground base station.

[0073] The airborne terminal determines the actual serving cell through the PCI and real-time location information of the serving cell, and controls the phased array antenna to point the beam to the serving cell, ready to receive the multiplexed frequency downlink data and communicate normally with the ground base station. Fig. 9 The airborne terminal service cell confirmation process includes the following steps:

[0074] Step 4.1: The airborne terminal obtains the PCI information of the accessed cell, selects cells using the same PCI from the pre-stored basic information of all ground-to-air system base stations, and generates a list of candidate service cells. Assume that there are k candidate service cells {1, 2, 3, …, k}.

[0075] Step 4.2: During the movement, the airborne terminal obtains the current position information of the aircraft (longitude X, latitude Y, altitude H) in real time through the GPS receiver.

[0076] Step 4.3: The airborne terminal calculates the distance D from the aircraft (or airborne terminal) to the candidate service cell i (i = 1, 2, ..., k) obtained above by using the Haversine formula below based on the current location information and the latitude and longitude information of the candidate service cell. i :

[0077]

[0078] Where X and Y are the real-time longitude and latitude obtained by the airborne terminal through the GPS receiver. i , Y i are the longitude and latitude of the ith candidate serving cell, and the radius of the earth is set to a constant R=6371km.

[0079] Step 4.4 The airborne terminal obtains the shortest distance D by comparing the distances calculated above. min , determine the shortest distance Dj The corresponding candidate serving cell j (1≤j≤k) is the actual serving cell of the airborne terminal.

[0080] D min =min(D i )=D j

[0081] Step 4.5: The airborne terminal calculates the relative angle between the current position of the aircraft (or airborne terminal) and the actual serving cell position using the following formula:

[0082] Angle α in the horizontal direction (0° in the north direction):

[0083] The vertical angle β (vertical to the center of the earth is 0°):

[0084] Where Y and H are the latitude and altitude of the airborne terminal, Y j , H j is the latitude and altitude of the actual service cell j, D j is the distance between the airborne terminal and the actual serving cell obtained in step 4.3.

[0085] Step 4.6: The airborne terminal controls the phased array antenna to point the beam to the actual service cell according to the relative angle data calculated in step 4.5, and prepares to receive the reused frequency downlink data.

[0086] The following is the increase in downlink rate obtained by simulation calculation when the ground-to-air broadband communication system reuses the operator's 3.5G frequency band 100MHz bandwidth.

[0087]

[0088] It can be seen from the above data that the present invention significantly increases the downlink transmission bandwidth of the ground-to-air communication system, and can provide more diversified data business services to more passengers to meet user experience.

[0089] In the present invention, no matter whether the reused frequency used is TDD or FDD, the reused frequency of the ground-to-air broadband communication network is only used for downlink (i.e., ground-to-air) unidirectional data transmission, reducing the types of interference caused by frequency reuse. At the same time, since services such as in-flight video and downloading also have a greater demand for downlink bandwidth, using it only for downlink can both meet business scenarios and improve spectrum utilization. In addition, the entire network uses reused frequencies of multiple frequency bands, at least 2. By flexibly using different reused frequencies in different areas and reasonably setting the spatial isolation of the same-frequency base stations between systems, the same-frequency interference caused by frequency reuse can be reduced. At the same time, the complexity of solution design and the construction cost are reduced, which is particularly suitable for scenarios where multiplexing operators jointly build and share frequency solutions.

[0090] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the present invention is not limited thereby. Any modification, equivalent substitution and improvement made by those skilled in the art without departing from the scope and essence of the present invention shall be within the scope of the present invention.

Claims

1. A method for implementing frequency reuse in a ground-to-air broadband communication system, characterized in that: The method comprises: Setting an uplink dedicated frequency and a downlink dedicated frequency for a ground-to-air broadband communication system, and multiple multiplexed frequencies used as aggregated downlink subcarriers, wherein the multiple multiplexed frequencies multiplex the frequencies of a ground operator system; According to the multiple reused frequencies of the ground-to-air broadband communication system and the ground operator system, a ground-to-air system base station spatially isolated from a ground co-frequency network base station of the ground operator system is deployed for the ground-to-air broadband communication system along the route; According to the coverage of multiple reuse frequencies in the ground operator system, selecting an actual reuse frequency for the deployed ground-to-air system base station from multiple reuse frequencies; The uplink dedicated frequency is used for air-to-ground communication of the ground-to-air broadband communication system, and the downlink dedicated frequency and the actual reuse frequency of the ground-to-air system base station are used for ground-to-air communication of the ground-to-air broadband communication system.

2. The frequency reuse method according to claim 1, characterized in that: The method of arranging a ground-to-air system base station spatially isolated from a ground co-frequency network base station of the ground operator system for the ground-to-air broadband communication system along the route according to the multiple reused frequencies of the ground-to-air broadband communication system and the ground operator system comprises: For any reused frequency of the ground-to-air broadband communication system and the ground operator system, determine the spatial isolation distance between the ground-to-air system base station of the ground-to-air broadband communication system and the ground co-frequency network base station of the ground operator system based on the reused frequency; According to the spatial isolation distance, a ground-to-air system base station spatially isolated from the ground co-frequency network base station of the ground-to-air broadband communication system is deployed along the route for the ground-to-air broadband communication system.

3. The frequency reuse method according to claim 1, characterized in that: The selecting, according to the coverage of the multiple reuse frequencies in the ground operator system, an actual reuse frequency for the deployed ground-to-air system base station from the multiple reuse frequencies comprises: Obtaining coverage of each of the multiple reuse frequencies of the terrestrial operator system; Dividing a plurality of regions according to the coverage of each of the plurality of multiplexing frequencies of the terrestrial operator system, wherein the coverage of the plurality of multiplexing frequencies of the terrestrial operator system in each region is different; For any area, the reuse frequency that minimizes the coverage of the ground operator system in the area is found from multiple reuse frequencies, and the found reuse frequency is used as the actual reuse frequency of the ground-to-air system base station deployed in the area.

4. The frequency reuse method according to claim 1, characterized in that: The method further comprises: Installing an airborne terminal having an airborne dedicated frequency transceiver module and an airborne multiplexed frequency receiving module on the aircraft, and configuring the actual multiplexed frequency for the airborne multiplexed frequency receiving module to receive a signal transmitted by the ground-to-air system base station using the actual multiplexed frequency; Installing an omnidirectional antenna connected to the airborne dedicated frequency transceiver module as an airborne dedicated frequency radio frequency antenna and installing a phased array antenna connected to the airborne multiplexed frequency receiving module as an airborne multiplexed frequency radio frequency antenna on the aircraft; The ground-to-air system base station is configured with an RRU and a directional antenna as a base station dedicated frequency RF module and an AAU as a base station multiplexing frequency transmission module, and the base station multiplexing frequency transmission module is configured with the actual multiplexing frequency to use the actual multiplexing frequency to transmit signals to the airborne terminal.

5. The frequency reuse method according to claim 4, characterized in that: The method further comprises: A data storage unit is provided in the airborne terminal, and basic information of all ground-to-air system base stations of the ground-to-air broadband communication system is pre-stored in the data storage module, wherein the basic information includes site name, base station ID, cell name, cell ID, cell PCI, location information, and supported frequency bands.

6. The frequency reuse method according to claim 4 or 5, characterized in that: Before using the uplink dedicated frequency to perform air-to-ground communication of the ground-to-air broadband communication system, and using the downlink dedicated frequency and the actual reuse frequency of the ground-to-air system base station to realize ground-to-air communication of the ground-to-air broadband communication system, the method further includes: The airborne terminal randomly accesses a cell of the ground-to-air broadband communication system by executing an initial network access process to obtain a reused frequency, or the airborne terminal obtains a reused frequency by executing an inter-cell handover process; The airborne terminal synchronously modifies the actual reuse frequency of its airborne reuse frequency receiving module according to the reuse frequency, and determines the actual serving cell by executing the serving cell confirmation process; The airborne terminal controls its airborne multiplexed frequency radio frequency antenna to direct the beam toward the actual serving cell, so as to achieve ground-to-air communication between the airborne terminal and the actual serving cell.

7. The frequency reuse method according to claim 6, characterized in that: The airborne terminal randomly accesses a cell of the ground-to-air broadband communication system by executing an initial network access process to obtain a reuse frequency, including: The airborne terminal performs a cell search on the downlink dedicated frequency to randomly access the searched and selected cell; The airborne terminal receives an RRC reconfiguration message of a random access cell, and acquires the reuse frequency from the RRC reconfiguration message.

8. The frequency reuse method according to claim 6, characterized in that: The airborne terminal acquires the reuse frequency by executing the inter-cell switching process, including: The airborne terminal performs co-frequency measurement, measures signals of surrounding dedicated frequencies and reports a measurement report; The airborne terminal receives an RRC reconfiguration message sent by the current cell after making an inter-cell handover decision according to the measurement report, and obtains information of a target cell to be handed over from the RRC reconfiguration message, wherein the target cell information includes a reuse frequency of the target cell; The airborne terminal performs random access to the target cell on a downlink dedicated frequency.

9. The frequency reuse method according to claim 6, characterized in that: The airborne terminal determines the actual serving cell by executing the inter-cell switching process: The airborne terminal obtains PCI information of the randomly accessed cell, selects cells using the same PCI from pre-stored basic information of all ground-to-air system base stations, and generates a candidate serving cell list; The airborne terminal calculates the distance between the airborne terminal and each candidate service cell according to the current position information obtained in real time by the GPS receiver during the movement of the aircraft and the position information of each candidate service cell in the candidate service cell list; The airborne terminal confirms the candidate serving cell corresponding to the shortest distance as the actual serving cell of the airborne terminal.

10. The frequency reuse method according to claim 6, characterized in that: The airborne terminal controls its airborne multiplexed frequency radio frequency antenna to direct a beam toward the actual serving cell, comprising: The airborne terminal determines the relative angle between the current position of the aircraft and the position of the actual serving cell according to the current position information acquired in real time by the GPS receiver during the movement of the aircraft and the position information of the actual serving cell; The airborne terminal controls the airborne multiplexing frequency radio frequency antenna to direct the beam to the actual serving cell according to the relative angle between the current position of the aircraft and the position of the actual serving cell.

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