Communication system and communication method

Abstract

This invention provides a communication system and a communication method. The communication method includes: obtaining a frequency domain compensation parameter and a time domain compensation parameter in advance via system parameters; and, after the main synchronization signal is broadcast, adjusting the original preset frequency band and preset time using the aforementioned compensation parameters, and receiving signals at a base station accordingly to compensate for frequency offset and time delay. In a preferred embodiment, the method further includes: calculating multiple similarity measures to determine whether a specific user equipment is active, and obtaining residual frequency error estimates and residual time error estimates corresponding to the specific user equipment through peak search. The estimates are then transmitted to the user equipment to provide necessary adjustments.

Description

Technical Field

[0001] This invention relates to a communication system technology, and more specifically, to a communication system and method suitable for use in non-terrestrial networks. Prior Technology

[0002] The Third Generation Partnership Project (3GPP) began exploring the integration of satellite communications with 5G terrestrial wireless networks in 2019, as revealed in documents TR 38.811 and TR 38.821, which are from versions 15 and 16, respectively. Subsequently, version 17 introduced a work project on 5G new radio (NR) for non-terrestrial networks (NTNs), and also conducted a research project focusing on supporting the application of the Narrowband Internet of Things (NB-IoT) protocol in non-terrestrial networks.

[0003] Narrowband IoT is a recently developed framework within the 3G Partner Program specifications, designed to accommodate a large number of user equipment (UEs) in massive machine-type communication (mMTC) scenarios. In this context, UEs transmit via a narrowband Physical Random Access Channel (NPRACH) preamble, similar to how mobile devices request resources through a random access (RA) procedure in mobile communication networks. The NB-IoT Physical Random Access Channel (NPRACH) consists of consecutive subcarriers allocated for preamble transmission. It is crucial for the base station (BS) to distinguish signals from different active UEs, identify these active UEs, and estimate the relevant channel parameters for individual uplinks.

[0004] Integrating Narrowband Internet of Things (NB-IoT) into non-terrestrial networks presents multiple challenges because existing NB-IoT specifications were originally designed for terrestrial networks (TNs) and do not account for the channel-disrupting characteristics of non-terrestrial networks, such as long propagation delays, significant Doppler shifts, and limited power availability. Making NB-IoT suitable for non-terrestrial networks may require modifications to the current protocol specifications. However, these adjustments must be kept as minimal as possible to ensure compatibility with existing 5G infrastructure. A key area of ​​potential change is the narrowband physical random access channel procedure, the current form of which fails to address satellite communication challenges such as long propagation delays and high Doppler shifts. While some recent research has addressed these challenges, further work is needed to meet the unique requirements of non-terrestrial network environments. Summary of the Invention

[0005] One of the preferred embodiments of the present invention aims to provide a communication system and communication method suitable for use in non-terrestrial networks, applicable to narrowband communication, applicable to non-terrestrial network communication, and compatible with terrestrial network communication.

[0006] Another object of the preferred embodiments of the present invention is to provide a communication system and communication method suitable for use in non-terrestrial networks, which can be used to increase the probability of random access in non-terrestrial networks.

[0007] Another objective of a preferred embodiment of the present invention is to provide a communication system and a communication method that allows a user device to modify the communication between the user device and the base station according to parameters provided by the base station after random access.

[0008] In view of this, a preferred embodiment of the present invention provides a communication system including a communication base station, which includes a detection and estimation unit and a dedicated channel transmission unit. The detection and estimation unit is configured to receive a received signal, perform a two-dimensional correlation function calculation on a plurality of user devices, and obtain a plurality of candidate values ​​for residual frequency errors and a plurality of candidate values ​​for residual time errors for each user device. Based on whether the plurality of similarity measurements corresponding to a user device exceed a threshold value, the unit determines whether the user device is in an active state. The dedicated channel transmission unit communicates with the detection and estimation unit and is configured to transmit a response to the user device deemed to be in an active state.

[0009] Another preferred embodiment of the present invention provides a communication system including a communication base station. The base station includes a compensation unit for transmitting a communication beam to the Earth's surface, wherein the communication beam covers a specific service area. Before the base station broadcasts a primary synchronization signal, the compensation unit acquires frequency domain compensation parameters and time domain compensation parameters pre-calculated and pre-stored by system parameters. After the primary synchronization signal is broadcast, the base station receives the received signal in a post-compensation frequency band and at a post-compensation time. The post-compensation frequency band is obtained by adjusting the frequency domain compensation parameters from a first preset frequency band in a specification, and the post-compensation time is obtained by adjusting the time domain compensation parameters from a first preset time in the specification, thereby compensating for frequency offsets and time delays caused by the Doppler effect.

[0010] According to a preferred embodiment of the communication system of the present invention, the main synchronization signal is defined in the specification as being broadcast on a second preset frequency band and within a second preset time period. The communication base station broadcasts the main synchronization signal in a pre-compensation frequency band and a pre-compensation time. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using frequency domain compensation parameters. The pre-compensation time is adjusted from the second preset time to the pre-compensation time using time domain compensation parameters.

[0011] Another preferred embodiment of the present invention provides a communication method, the communication method comprising: receiving a received signal; performing a two-dimensional correlation function calculation on a plurality of user devices and obtaining a plurality of residual frequency error candidate values ​​and a plurality of similarity measures for a plurality of residual time error candidate values ​​for each user device; determining whether a user device is in an active state based on whether the plurality of similarity measures corresponding to a user device exceed a threshold value; and transmitting a response to the user device that is considered to be in an active state.

[0012] Another preferred embodiment of the present invention provides a communication method, which includes: before broadcasting a main synchronization signal, acquiring a frequency domain compensation parameter and a time domain compensation parameter pre-calculated and pre-stored by system parameters; after the main synchronization signal is broadcast, receiving a received signal in a post-compensation frequency band and a post-compensation time, wherein the post-compensation frequency band is obtained by adjusting the frequency domain compensation parameter from a first preset frequency band in a specification, and the post-compensation time is obtained by adjusting the time domain compensation parameter from a first preset time in the specification, thereby compensating for frequency offsets affected by the Doppler effect and long delays caused by long distances between the transmitter and receiver.

[0013] According to a preferred embodiment of the communication method of the present invention, the main synchronization signal is defined in the specification as being broadcast on a second preset frequency band and within a second preset time period. The communication method further includes: broadcasting the main synchronization signal in a pre-compensation frequency band and a pre-compensation time period, wherein the pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using a frequency domain compensation parameter, and the pre-compensation time is adjusted from the second preset time to the pre-compensation time using a time domain compensation parameter.

[0014] A preferred embodiment of the present invention proposes pre-compensation and post-compensation schemes for both the frequency and time domains, ensuring that the non-terrestrial network communication base station can effectively receive random access requests from terrestrial user equipment without altering the user equipment specifications. In another preferred embodiment, by performing two-dimensional similarity measurement calculations on multiple residual frequency error candidate values ​​and multiple residual time error candidate values ​​for each user equipment, the communication base station can accurately identify active user equipment, thereby improving the success rate of random access requests from user equipment. Furthermore, the two-dimensional similarity measurement calculation in this embodiment can also obtain residual frequency error estimates and residual time error estimates. The communication base station can transmit these values ​​to each active user equipment, allowing each user equipment to adjust its frequency and time to improve communication quality suitable for non-terrestrial networks (NTNs).

[0015] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Simple Explanation of the Diagram

[0016] The accompanying drawings are provided to enable those skilled in the art to further understand the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the invention and are used, together with the specification, to explain the principles of the invention.

[0017] Figure 1 illustrates a system schematic diagram of a preferred embodiment of the present invention, suitable for use in a communication system for non-terrestrial networks (NTN).

[0018] Figure 2 illustrates a geometrical diagram of a low Earth Orbit (LEO) satellite operating scenario suitable for a communication system used in a non-terrestrial network (NTN) according to a preferred embodiment of the present invention.

[0019] Figure 3 illustrates the relationship between elevation angle and beam spot size of a communication system suitable for use in a non-terrestrial network (NTN) according to a preferred embodiment of the present invention.

[0020] Figure 4 illustrates a schematic diagram of frequency domain pre-compensation and post-compensation for uplink and downlink communication between a communication base station and a user device according to a preferred embodiment of the present invention.

[0021] Figure 5 illustrates a schematic diagram of the "pre-compensation" and "post-compensation" in the time domain of a preferred embodiment of the present invention, suitable for use in a communication system for non-terrestrial networks (NTN).

[0022] Figure 6 illustrates a system schematic diagram of a preferred embodiment of the present invention, suitable for use in a communication system for non-terrestrial networks (NTN).

[0023] Figure 7 illustrates a simulation diagram of similarity measurement suitable for communication systems used in non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention.

[0024] Figure 8 illustrates a circuit block diagram of a detection and estimation unit 603 suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention.

[0025] Figure 9 illustrates a circuit block diagram of a single random access channel (mono-RACH) similarity measurement calculation unit 801 suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention.

[0026] Figure 10 illustrates a circuit block diagram of the nth symbol-level correlator group 90n, which is suitable for use in a communication system for non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention.

[0027] Figure 11 illustrates a circuit block diagram of a detection and estimation unit 603 suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention.

[0028] Figure 12 illustrates a circuit block diagram of the omni-RACH correlator group 1102 of the detection and estimation unit 603, which is suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention.

[0029] Figure 13 illustrates a simulated environment for similarity measurement of a communication system suitable for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention.

[0030] Figure 14 illustrates a simulation diagram of similarity measurement suitable for communication systems used in non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention.

[0031] Figure 15 illustrates a flowchart of pre-compensation and post-compensation for a communication method suitable for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention.

[0032] Figure 16 illustrates a flowchart of a user equipment identification method suitable for a communication method used in a non-terrestrial network (NTN) according to a preferred embodiment of the present invention.

[0033] Figure 17 illustrates a sub-step flowchart of step S1603 of a communication method suitable for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention for identifying user equipment.

[0034] Figure 18 illustrates a sub-step flowchart of step S1603 of a communication method suitable for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention for identifying user equipment. Implementation

[0035] The present invention will be described in detail with reference to exemplary embodiments, which are illustrated in the accompanying drawings. Where possible, the same element symbols are used in the drawings and description to refer to the same or similar parts. Furthermore, the exemplary embodiments are merely one way of implementing the design concept of the present invention, and the following examples are not intended to limit the scope of the invention.

[0036] In the context of the rapid development of wireless communication technology, 3GPP standards have become an important foundation for global mobile communication systems. However, when it comes to non-terrestrial network communication, especially narrowband Internet of Things (NB-IoT), current 3GPP technology faces significant challenges. While the narrowband nature of NB-IoT helps extend device battery life and improve spectral efficiency, it also leads to significant inter-channel interference (ICI). This interference is particularly severe in high-speed satellite communication environments because the frequency shift of the received signal is quite high with the rapid movement of satellites, further exacerbating the impact of ICI. Furthermore, due to the Doppler effect, signal reception and timing synchronization during random access become more difficult. These problems often cause NB-IoT devices to fail to establish connections, reducing the overall system reliability and performance.

[0037] Non-terrestrial network (NTN) communication systems, especially today's 5th generation wireless communication networks, suffer from severe Doppler effect due to the narrowband nature of the Internet of Things (IoT), particularly the extremely high speed of satellites. The relative motion between the signal source (e.g., satellite) and the receiver (e.g., ground station or user equipment) causes significant frequency shifts, resulting in a mismatch between the received signal frequency and the pre-defined receiving frequency. Furthermore, the significantly higher altitude of satellites compared to traditional terrestrial base stations leads to a substantial increase in propagation delay.

[0038] Frequency offset can be detrimental to user equipment using Physical Random Access Channel (PRACH) because the channel bandwidth is relatively wide, allowing for random access to the communication base station. However, for user equipment using Narrowband IoT Physical Random Access Channel (NPRACH), this effect is fatal, as such frequency offset can prevent the signals transmitted by the Narrowband IoT user equipment from accessing the communication base station at all.

[0039] Furthermore, considering propagation delay, the 3GPP standard specifies that at each preset time interval, the base station must send a primary synchronization signal (PSS). Additionally, the user equipment (UE) uses the received PSS to accurately obtain the cell's synchronization information. Within a specified time period (one frame or several time slots) after the base station sends the PSS, a receiving window is subsequently opened. During this time, the base station prepares to receive narrowband IoT physical random access channel (PRAM) signals from the UE. Due to the Doppler effect, the PSS is subject to frequency offset, and the UE's narrowband PRAM signals are also delayed over long distances. Therefore, the base station often fails to receive any signal within the specified receiving window.

[0040] Figure 1 illustrates a system schematic diagram of a communication system suitable for non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention. Referring to Figure 1, in this embodiment, the communication system suitable for non-terrestrial networks (NTNs) is exemplified by a current 5th Generation wireless communication network, and specifically by Narrowband Internet of Things (NB-IoT). In Figure 1, this communication system includes a communication base station 101 located on a satellite, and it is assumed that there are two user equipment UE0 and UE1 within the service area of ​​the communication base station 101.

[0041] In Narrowband Internet of Things (NB-IoT), the base station needs to establish a connection with the user equipment through a random access (RA) procedure. During the RA procedure, the base station 101 first sends a Primary Synchronization Signal (PSS). In this embodiment, the primary synchronization signal is exemplified by the Narrowband Primary Synchronization Signal (NPSS). Those skilled in the art will understand, after referring to the embodiments of this invention, that this invention is also applicable to general user equipment; therefore, this invention is not limited thereto, and PSS is simply used as a descriptive term below. After receiving the PSS, the user equipment within the base station's service area performs time and frequency synchronization and sends a preamble to the base station during the random access opportunity (RAO) period. In other words, the base station 101 needs to broadcast the primary synchronization signal (PSS) at fixed intervals. Furthermore, the user equipment accurately obtains synchronization information within the service area by receiving the primary synchronization signal. Within a specified time period (one frame or several time slots) after the communication base station 101 transmits the primary synchronization signal (PSS), a receiving window will be opened. During this period, the base station prepares to receive the narrowband physical random access channel (NPRACH) preamble signal from the user equipment. Due to the distance between the satellite and the ground, the primary synchronization signal is delayed in propagation, and the NPRACH preamble signal from the user equipment is also frequency-shifted. As a result, the communication base station 101 often fails to receive any signal within the specified receiving window and on the specified frequency band, leading to random access failure.

[0042] To mitigate / compensate the aforementioned effects, in this embodiment, the communication base station 101 includes a compensation unit to perform both "pre-compensation" and "post-compensation" measures. First, referring to Figure 1, in this embodiment, the communication base station 101 is exemplified as a satellite communication base station, transmitting a communication beam to the Earth's surface, covering a specific service area within a beam spot. In this embodiment, the working scenarios shown in Figure 1 are employed, and further analysis is performed based on the parameter settings in Table 1 below. [Parameters] [Setting 1] [Setting 2] Altitude h sat = 600 km h sat = 600 km Payload Regenerative Regenerative Operating band S-band (2 GHz) <00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Since regenerative payloads were selected in settings 1 and 2, these payloads can operate as next-generation communication nodes (NodeB / gNB). An overview of the Low Earth Orbit (LEO) operating scenario is shown in Figure 2. Figure 2 illustrates a geometrical diagram of a LEO satellite operating scenario suitable for a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention. Referring to Figure 2, the observation slant range is calculated based on the elevation angle of the user equipment (UE). Using the auxiliary lines shown in the figure, the equation can be rearranged using Pythagorean theorem as shown in equation (1): ...(1)

[0044] in, A meter represents the Earth's radius. The altitude of the serving satellite is represented by θ, and θ0 represents the elevation angle of the user equipment (UE). After obtaining the distance between the UE and the satellite from equation (1) above, the signal propagation delay, also known as the time of arrival (ToA), can be calculated. Where C is the speed of light. .

[0045] Figure 3 illustrates the relationship between elevation angle and beam spot size in a preferred embodiment of the present invention suitable for a communication system used in a non-terrestrial network (NTN). Referring to Figure 3, using the above-mentioned equation (1) and the beam layout described in Figure 3, and iteratively applying the cosine theorem, the maximum and minimum propagation delays within the beam spot can be calculated, and the results are listed in Table 2. Additionally, the maximum excess timing delays have also been calculated and are listed in Table 2. From the calculated values ​​in Table 2, a common delay can be estimated for the aforementioned "pre-compensation" and "post-compensation" in the time domain. Both of these are performed at the base station receiver on the satellite. Setting 1 Setting 2 Minimum Spot Diameter Max. Delay Min. Delay Max. Excess Spot Diameter Max. Delay Min. Delay Max. Excess Elevation Angle (km) Dmax (ms) Dmin (ms) Delay (μs) (km) Dmax (ms) Dmin (ms) Delay (μs) 30 o(π∕6 rad) 144.02 3.5836 3.1770 406.67 256.91 3.5836 2.8741 709.5606 45 o(π∕4 rad) 82.10 2.7160 2.5299 186.10 153.63 2.7160 2.3816 334.4198 90 o(π∕2 rad) 46.23 2.0015 2.0000 1.4836 92.70 2.0061 2.0000 5.9583 Table II

[0046] Please refer back to Figure 2. Considering the geometric position in Figure 2, we can obtain the following equation: ...............(2) Equation (2) above can be rearranged into the following equation: ..............(3)

[0047] Therefore, 2 can be explicitly represented as a function of 0, and vice versa, as follows: ...............(4)

[0048] Therefore, the Doppler frequency is calculated as follows: ..........(5)

[0049] in, The instantaneous tangential velocity of the satellite, For gravitational acceleration, The maximum Doppler frequency is denoted by C, and fc represents the speed of light and the carrier frequency, respectively.

[0050] Using equation (5) above and iteratively applying the cosine theorem, the maximum and minimum Doppler frequencies within the beam spot can be calculated, and the results are listed in Table 3. A common Doppler offset can be estimated from the calculated values ​​of the maximum and minimum Doppler frequencies in Table 3, which is used for the aforementioned "pre-compensation" and "post-compensation" in the frequency domain. In this embodiment, the algebraic average of the maximum and minimum Doppler frequencies is preset as the common Doppler offset. Setting 1 Setting 2 Minimum Diameter Maximum Minimum Mean Residual Diameter Maximum Minimum Mean Residual Elevation Angle (km) (kHz) (kHz) (kHz) (kHz) (km) (kHz) (kHz) (kHz) (kHz) 30 o(π∕6 rad) 144.02 43.6126 41.5855 42.5991 ±1.0136 256.91 43.6126 39.3746 41.4936 ±2.1190 45 o(π∕4 rad) 82.10 35.6096 32.7815 34.1955 ±1.414 153.63 35.6096 29.7813 32.6954 ±2.9142 90 o(π∕2 rad) 46.23 1.9387 -1.9387 0.0 ±1.9387 92.70 3.8800 -3.8800 0.0 ±3.8800 Table 3

[0051] For example, the user equipment in Figure 1 is located at the satellite's minimum elevation angle. At that time, the Earth's radius Satellite altitude Satellite speed The user equipment's speed is extremely low and negligible compared to the satellite's movement speed. In this case, the Doppler frequency observed by the user equipment is:

[0052] This degree of Doppler frequency shift causes the received signal to be shifted out of the frequency band, making it impossible to receive and detect correctly. Therefore, this invention proposes to pre-compensate for the Doppler shift when the base station transmits the main synchronization signal to reduce the impact on the receiver. In this embodiment, the base station 101 performs pre-compensation on a beam range basis, meaning that all user equipment within the same service range receives the same compensation. In this embodiment, the algebraic average of the highest and lowest Doppler frequencies within the beam range is set as the common Doppler frequency. In this embodiment of the invention, since the base station can obtain the satellite's system parameters, such as the satellite's current altitude, position, and the angle between it and the ground (as shown in Table 3 above, which has been pre-calculated), the common Doppler frequency can be obtained. .

[0053] For ease of explanation, the actual Doppler frequency shift of the user equipment is assumed to be... In other words, after subtracting the common Doppler frequency from the actual Doppler frequency shift, the remaining Doppler frequency shift depends on the location of the user equipment (UE).

[0054] Figure 4 illustrates a schematic diagram of frequency domain pre-compensation and post-compensation for uplink and downlink communication between a communication base station and a user equipment according to a preferred embodiment of the present invention. Referring to Figure 4, according to the Narrowband Internet of Things (NB-IoT) specification, the communication base station 101 needs to transmit a primary synchronization signal at fixed intervals. To address severe Doppler frequency offset, before transmitting the primary synchronization signal PSS, the communication base station 101 (gNB) pre-compensates the frequency of the primary synchronization signal to be transmitted from the downlink reference frequency in the original specification to the aforementioned common Doppler frequency. Here, it is assumed that the communication base station 101 has an error of a local oscillator. Therefore, the frequency error of the primary synchronization signal PSS broadcast by communication base station 101 will be transformed into... The aforementioned common Doppler frequencies The compensation unit, which can be pre-calculated and pre-stored within the communication base station 101, serves as a frequency domain compensation parameter. Therefore, in this case, it's equivalent to adjusting the originally preset frequency band to the pre-compensated frequency band using the frequency domain compensation parameter. After passing through a non-terrestrial transmission channel, the frequency error of the broadcast primary synchronization signal (PSS) will be transformed... .

[0055] After the user equipment receives the primary synchronization signal (PSS), its local oscillator aligns with the frequency and time of the received PSS; assuming the frequency error caused by the user equipment during alignment is... At this point, the frequency error of the user equipment will be transformed into... According to the frequency-division duplex (FDD) specification of Narrowband Internet of Things (NB-IoT), the frequency spacing between the downlink reference frequency and the uplink reference frequency is: Therefore, during the random access opportunity (RAO) period, the user equipment uses a frequency aligned with the primary synchronization signal (PSS) plus a frequency division duplex interval. Subsequently, the preamble is transmitted to communication base station 101 via the Narrowband Physical Random Access Channel (NPRACH). At this time, in the uplink, the frequency error of the user equipment is... This error is based on the downlink reference frequency specified in the standard.

[0056] Next, the signal containing the preamble is transmitted to communication base station 101. Also affected by the Doppler frequency shift, the signal frequency error received by the base station is... In this embodiment, the communication base station 101 communicates via the aforementioned common Doppler frequency. Frequency compensation is performed, meaning that the communication base station 101 will standardize the preset uplink receiving frequency band. Move to The frequency band receives uplink signals, and here, it is also done through the frequency domain compensation parameters (that is, the aforementioned common Doppler frequency) of the compensation unit pre-stored in the communication base station 101. The original preset frequency band is adjusted to the post-compensation frequency band. At this point, the residual frequency error of the signal after the above post-compensation can be expressed as follows: ...(6)

[0057] As can be seen from the derivation in Figure 4 above, the residual frequency error generated during narrowband Physical Random Access Channel (NPRACH) reception can be calculated as follows: In NTN, the frequency error generated during narrowband Physical Random Access Channel (NPRACH) reception has been calculated and listed in Table 4. Additionally, the rightmost column of Table 4 shows the frequency error obtained by prior art through compensation at the user end. As can be seen from Table 4, the frequency error after applying the "pre-compensation" and "post-compensation" methods proposed in this embodiment is significantly lower than the frequency error obtained by prior art through compensation at the user end. Setting 1 Setting 2 Minimum Diameter 2(X-X̅)+ε 2( X-X̅) ±ε Diameter 2( X-X̅) +ε 2 ( X-X̅) + ε XU + ε 仰角 (千米) (千赫兹) ( ) (千米) (千赫兹) (<00s0413>) (千赫兹) 30°(π∕6弧度) 144.02<00004:17>±2.1772 [[ID=2?]]±0.5806 256.91 ±4.3880 ±1.1701 ±20.15 45°(π∕4弧度) 82.10 ±2.9780 ±0.7941 153.63 ±5.9784 ±1.5942 ±20. I5 90°(π∕2弧度) 46.23 ±4.0274 ±1.0740 92.70 ±7.9100 ±2.1093 ±20.15 Table 4

[0058] It should be noted that there seems to be a small error in the "00s0413" in the original text, which is assumed to be "0000413" for translation.As explained above, after the aforementioned "pre-compensation" and "post-compensation" of the frequency, the frequency error of the signal received by the base station is significantly reduced. Furthermore, in this embodiment, both "pre-compensation" and "post-compensation" are performed within the base station on the satellite. For the user equipment (UE), only the original work of a terrestrial network UE is performed: synchronizing its receiver's local oscillator to the received primary synchronization signal (PSS), and then transmitting the preamble preset by the specification based on the synchronized data. Therefore, the UE does not know whether the received primary synchronization signal PSS comes from a terrestrial network (TN) base station or from a non-terrestrial network (NTN) base station broadcast. Therefore, the technique of pre-compensating the transmitted signal by the gNB in ​​the non-terrestrial network (NTN) using a common Doppler frequency before transmitting the signal maintains backward compatibility with the terrestrial network (TN) specified in 3GPP.

[0059] Another major challenge of non-terrestrial network communication is high propagation delays. According to the calculation in equation (1) and Table 2, the maximum and minimum propagation delays occur at elevation angles of 30° and 90°, respectively, with propagation delays of 3.58 ms and 2.00 ms. Such propagation delays are even greater than the length of a preamble. To eliminate propagation delays in non-terrestrial networks (NTNs), this embodiment proposes a time-domain "pre-compensation" and "post-compensation" performed in base station 101.

[0060] Figure 5 illustrates the operation of "pre-compensation" and "post-compensation" in the time domain of a preferred embodiment of the present invention suitable for a non-terrestrial network (NTN) communication system. Referring to Figure 5, reference numeral 501 is the time domain operation diagram of a non-terrestrial network according to a preferred embodiment of the present invention; reference numeral 502 is the time domain operation diagram of a 3GPP terrestrial network; and reference numeral 503 is the time domain operation diagram of a communication base station in a non-terrestrial network according to a preferred embodiment of the present invention. In this embodiment, a downlink signal frame consists of 10 subframes of 1ms length, and each subframe consists of 2 timeslots of 0.5ms length, with each timeslot consisting of 7 symbols. The narrowband main synchronization signal NPSS is located in the sixth subframe and is broadcast once per frame. When the satellite-based communication base station 101 broadcasts the narrowband primary synchronization signal (NPSS) to all user equipment (UEs) within its beam, time advance (Pre-TA) is performed before uplink transmission. Refer to the time-domain operation diagram 503 for non-terrestrial network communication base stations. Diagram 503 shows the actual transmission time sequence Tx, the actual reception time sequence Rx, and the standard specification time sequence on-time. These time sequences are typically implemented in hardware using temporary registers. In this embodiment, the NPSS transmission time is specified in the standard specification time sequence on-time. In the actual transmission time sequence Tx, the NPSS transmission is advanced by several sub-frames. The sub-frames of the NPSS received by user equipment UE0 and UE1 are precisely aligned with the standard specification time sequence on-time. In the next subframe after receiving the Narrowband Primary Synchronization Signal (NPSS), User Equipment (UE0) and User Equipment (UE1) can transmit the Narrowband Physical Random Access Channel (NPRACH) preambles NPRACH0 and NPRACH1. This period, referred to in the standard specification time series, is the period of Random Access Opportunity (RAO). Since UE0 and UE1 experience another propagation delay when transmitting the preamble to the satellite, the RAO in the communication base station is postponed (Post-TD) in this embodiment. This ensures that the Narrowband Physical Random Access Channel (NPRACH) preambles NPRACH0 and NPRACH1 are transmitted to the communication base station precisely within the postponed receiving window.

[0061] In this embodiment, for ease of explanation, the aforementioned times (Pre-TA) and (Post-TD) are, for example, set to a common delay of the same value. In this embodiment, the actual value of this common delay is, for example, set to the minimum propagation delay within the beam range. Since the communication base station 101 in the satellite knows the current altitude, position, and angle relationship between the satellite and the ground, as shown in Table 2 above, the aforementioned common delay is obtained. For example, if the relevant parameters of the satellite are at the aforementioned setting 1, the common delay will be set to, for example, 2.00 ms by looking up the table, for the "pre-compensation" and "post-compensation" shown in Figure 5. Although the times (Pre-TA) and (Post-TD) in the above embodiment are set to a common delay of the same value, and the common delay is set to the minimum propagation delay within the beam range, those skilled in the art should understand that the present invention does not limit the setting values ​​of the times (Pre-TA) and (Post-TD), and the times (Pre-TA) and (Post-TD) can also be, for example, the arithmetic mean of the maximum and minimum propagation delays. Those skilled in the art should understand that the present invention does not limit the set values ​​of time (Pre-TA) and (Post-TD) to integer multiples of the timeslot length.

[0062] The random access procedure is initiated after the user equipment acquires the primary synchronization signal (NPSS). Signals from communication base station 101 on the satellite must undergo pre-time advance (Pre-TA) to compensate for common delay. The PSS received by UE0 and UE1 may be delayed. Each UE independently estimates the time and frequency errors and then synchronizes with the received Narrowband Primary Synchronization Signal (NPSS). Therefore, in the diagram, UE0 and UE1 transmit their Narrowband Physical Random Access Path (NPRACH) preambles NPRACH0 and NPRACH1 at different times. Generally, this processing time is shorter than the subframe duration. UE0 and UE1 then transmit their Narrowband Physical Random Access Path (NPRACH) preambles NPRACH0 and NPRACH1 in the next subframe, at which point UE0 and UE1 consider this subframe as a Random Access Opportunity (RAO).

[0063] Next, please refer to the actual reception time series Rx in the time domain operation diagram 503 of the communication base station. In the reception sequence of the communication base station on the satellite, the receiving window of the random access opportunity (RAO) is delayed by a common delay. The preambles NPRACH0 and NPRACH1 arrive at the satellite communication base station during the delayed random access opportunity (RAO) reception window.

[0064] Next, as shown in the lower half of Figure 5, comparing it with the time-domain operation diagram 502 of the 3GPP terrestrial network, User Equipment 2 receives the Narrowband Primary Synchronization Signal (NPSS) broadcast from the ground base station eNB, and then transmits the Narrowband Physical Random Access Channel (NPRACH) preamble (NPRACH2) back to the ground base station eNB in ​​the next sub-frame. From a time perspective, the technology proposed in the preferred embodiment of this invention remains backward compatible with 3GPP. It is worth noting that through common delay... The achieved pre-time advance (pre-TA) can be considered as a delay in the transmission of the narrowband primary synchronization signal (NPSS), because the narrowband primary synchronization signal NPSS is based on... The periodic broadcast, where the period is the length of the 5G New Radio (NR) frame duration in non-terrestrial networks (NTNs). Simultaneously, the RAO delay should be implemented by delaying the RAO window. In particular, for transparent payloads, such as non-terrestrial satellites operating as analog radio frequency repeaters, the propagation delay and Doppler offset occurring in the feeder link between the ground base station and the satellite can be compensated or adjusted by the ground base station. The adjustment can also be achieved through pre-calculation and pre-stored data at the base station, but the compensation method will include the time and frequency from the ground base station to the satellite plus the time and frequency from the satellite to the user equipment. Ground base stations possess powerful computing capabilities, real-time ephemeris and beam-satellite geometry information, and high-precision local oscillators.

[0065] The above embodiments already ensure that: 1. The primary synchronization signal (PSS) sent by the communication base station 101 can be received by any user equipment within its service area within the specified time (e.g., 5G network specifications). 2. The received signal by the communication base station 101 under the adjusted post-compensation time and post-compensation frequency will include signals sent by user equipment within its service area, such as random access requests. However, due to the Doppler effect, the received random access requests will still experience frequency shift, causing the communication base station 101 to be unable to decode the random access requests, which is particularly fatal for user equipment using narrowband IoT Physical Random Access Channel (NPRACH).

[0066] For ease of explanation, this embodiment will be described below in discrete time format. The baseband equivalent signal transmitted by a user equipment is represented as follows: ...(7)

[0067] in, Indicates time index, Indicates the instantaneous time of sampling. For the sampling period, and , and These represent the sampling period and the symbol length, respectively. and These represent the number of samples in the cyclic prefix (CP) and the number of samples in the symbol group (SG), respectively. This indicates signal power, while This represents the energy of the signal during the sampling time; Indicates from the The first user device The subcarrier frequencies used in a symbol tuple (SG); and These are the floor operator and the modulo operator, for example, as well as They represent The integer part and the remainder part.

[0068] The superimposed signal received by the base station can be represented as: ...(8) in, .

[0069] Represents a complex number of channels. Indicates the normalized frequency error. Indicates the first The time error that occurs in the uplink This represents the initial phase error caused by the non-homogeneous frequency reduction process at the front end. For simplification, we use... Perform power normalization on the above equations. The normalized frequency error in equation (8) It is relative to the subchannel bandwidth (also known as subcarrier spacing). The normalized residual frequency error is defined as follows: .

[0070] in, Indicates the first The residual frequency error of each uplink, in Hertz (Hz). The calculated values ​​are listed in rows 3 and 6 of Table 4, while the normalized frequency error... It has also been calculated and is listed in rows four and seven of Table 4. express At any moment The sampled additive white Gaussian noise (AWGN) has a power spectral density (PSD) of: The zero-to-zero bandwidth of the receiving filter here is... Therefore, sampling noise It has a mean of zero and a variance of . An uncorrelated Gaussian sequence. Due to the normalization relation. , It has a mean of zero and a variance of . Uncorrelated Gaussian sequences.

[0071] For the For a user device, the received signal in equation (8) above can be rewritten as: ...(9)

[0072] Wherein, the first term represents the term from the first term. The preamble of a user device is the expected signal item, and the subsequent item... Then it is:

[0073] This expression includes an inter-carrier interference (ICI) term, which is expressed as follows:

[0074] The term represents a term with a mean of zero and a variance of 0. Additive white Gaussian noise (AWGN). Inter-channel interference mainly originates from adjacent channels, and there is no explicit analytical model. The following analysis focuses primarily on the impact of the additive white Gaussian noise (AWGN) term. When the channel gain is... and initial phase When considered as a non-demand parameter, the first In the uplink and The similarity function and the log-likelihood function can be written in the following forms: ...(10) ...(11).

[0075] Therefore, it includes interference parameters. and ​ , and The joint maximum likelihood estimation (JMLE) can be written as: ...(12).

[0076] It is worth noting that the above equation (12) as well as This is unrelated to the search for the maximum value. Therefore, the output of the time-domain correlation operation can be represented as follows: ...(13)

[0077] Among them, the residual frequency error estimate and residual time error estimate Indicates the estimated first Frequency errors occurring in the uplink and the Timing errors occurring in the uplink .

[0078] Joint Maximum Similarity Estimation (JMLE) aims to find the th value when the maximum value is reached. Frequency errors occurring in the uplink and the Timing errors occurring in the uplink In this embodiment, for example, symbol-level correlation (SLC) can be used to achieve the joint maximum similarity estimation (JMLE). In this embodiment, an example is taken with m symbol groups (SG), and each symbol group (SG) has q symbols.

[0079] When applied to the qth symbol of the mth symbol group of the lth preamble of the uth user device, the Joint Maximum Similarity Estimation (JMLE) can be expressed as: …(14) Where m=0, 1, 2, 3; q=0, 1, 2, 3, 4. in, This is the desired term; This indicates inter-channel interference (ICI). This indicates noise.

[0080] The part requested It can be represented as follows:

[0081] Inter-channel interference (ICI) section It can be represented as follows:

[0082] For the noise section, we assume it to be additive white Gaussian noise (AWGN), and we will ignore the derivation details here.

[0083] Through the above Symbol Rank Correlation (SLC) method, the similarity measure detection on L preambles can be expressed as the accumulation of the squared magnitudes of the SLC output, as follows: …(15) in,

[0084] By using the possible u-th user device as well as By inputting each value, you can obtain the two-dimensional similarity measure results. Then, by finding the maximum value among these results, you can find the value corresponding to the maximum value. as well as Thus, the Joint Maximum Similarity Estimation (JMLE) is achieved. When the two-dimensional similarity measure result exceeds a set threshold, it indicates that the u-th user device has a high probability of being active. The maximum value of the two-dimensional similarity measure result corresponds to... as well as These are estimates of frequency and time errors. The base station can then issue a random access response to user equipment that is in an active state.

[0085] As described above, Figure 6 illustrates a system schematic diagram of a preferred embodiment of the present invention suitable for a communication system used in a non-terrestrial network (NTN). Referring to Figure 6, in this embodiment, the communication system suitable for a non-terrestrial network (NTN) is also exemplified by a current 5th Generation wireless communication network, specifically a narrowband Internet of Things (NB-IoT). This communication system suitable for a non-terrestrial network (NTN) includes a communication base station 601 and a service area 602. It is assumed here that this service area 602 includes a plurality of narrowband IoT user devices. The communication base station 601 is also exemplified by a satellite base station. This communication base station 601 includes a detection and estimation unit 603 and a dedicated channel transmission unit 604.

[0086] Communication base station 601 is used to open a receiving window to receive a signal within, for example, the 3GPP specification time, or the post-compensation time as described above. The detection and estimation unit 603 receives the aforementioned received signal. The system performs a two-dimensional correlation function calculation for each of the numerous user devices that can access the communication base station 601. In previous technologies, the communication base station 601 would only perform a one-time, simple one-dimensional correlation function calculation for each of the numerous user devices that could access the network to determine whether the corresponding user device had submitted a random access request. However, this communication base station 601, suitable for non-terrestrial networks (NTNs), is severely affected by the Doppler effect, and once user devices in narrowband IoT experience frequency offsets, they will enter non-standard channels. Therefore, simply using the one-dimensional correlation function calculation of previous technologies will be completely insufficient to confirm whether a user device is active.

[0087] In this embodiment, by using the above-mentioned two-dimensional correlation function calculation, and by performing multiple similarity measurements on multiple user equipment, multiple candidate values ​​of residual frequency error and multiple candidate values ​​of residual time error, the absolute value measurement of the spectral bins of each user equipment can be obtained. This is the similarity measurement.

[0088] Figure 7 illustrates a simulation diagram of similarity measurement suitable for a communication system in a non-terrestrial network (NTN) according to a preferred embodiment of the present invention. As shown in Figure 7 above, the X-axis represents the residual frequency error, the Y-axis represents the residual time error, and the Z-axis represents the absolute value measurement of spectral bins. If the absolute value measurement of any spectral bin, i.e., the similarity measurement, is greater than a predefined threshold, it indicates that a user equipment is active at the corresponding frequency and time. A random access response (RAR) can then be generated for this user equipment. This significantly reduces the detection error probability of the communication base station 601 and increases the access success rate of user equipment. The dedicated channel transmission unit 604 communicates with the detection and estimation unit 603 and is responsible for transmitting a response, such as a random access response (RAR), to user equipment deemed active. When the similarity measurement of user equipment does not exceed the set threshold, the detection and estimation unit 603 will determine that the user equipment is inactive, and the random access response (RAR) will not be sent.

[0089] In a further preferred embodiment, the detection and estimation unit 603 identifies the maximum value among multiple similarity measures of the active user equipment. Specifically, the detection and estimation unit 603 performs a peak search on the candidate values ​​of the residual frequency error and residual time error for the aforementioned similarity measures to obtain the estimated residual frequency error and residual time error corresponding to the user equipment. At this time, the communication base station 601 can also transmit the aforementioned estimated residual frequency error and residual time error to the corresponding user equipment through the dedicated channel transmission unit 604. Thus, the user equipment can adjust the transmission frequency and time based on the received estimated residual frequency error and residual time error, thereby improving communication quality.

[0090] Figure 8 illustrates a circuit block diagram of a detection and estimation unit 603 suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention. Referring to Figure 8, in this embodiment, the detection and estimation unit 603 includes a plurality of single random access channel (mono-RACH) similarity measurement calculation units 801. In this embodiment, the single random access channel (mono-RACH) similarity measurement calculation units 801 receive the aforementioned received signal. And the preambles corresponding to different random access channels. Preamble This can be considered an important criterion for determining whether a user equipment (UE) is connected. The UE will randomly select a preamble from the available preamble set according to a certain random algorithm. Therefore, in this embodiment, a preamble is used. As input to the single random access channel (mono-RACH) similarity measurement calculation unit 801, and using the received signal and preamble Perform relevant function calculations to determine whether the user's device is active.

[0091] Figure 9 illustrates a circuit block diagram of a single random access channel (mono-RACH) similarity measurement calculation unit 801 suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention. Referring to Figure 9, the single random access channel similarity measurement calculation unit 801 includes a plurality of symbol-level correlator banks (SLC banks) 900, 901, 902-90n. The first input terminal of each symbol-level correlator bank 900-90n receives the received signal. The second input of the zeroth symbol level correlator group 900 receives the undelayed preamble. The second input of the first symbol-level correlator group 901 receives a preamble delayed by one unit time. The second input of the second symbol level correlator group 902 receives a preamble delayed by two units of time. The second input of the nth symbol level correlator group 90n receives the preamble delayed by one unit time. Each symbol level correlator group 900~90n outputs multiple similarity metrics X NC corresponding to the delay time.

[0092] Figure 10 illustrates a circuit block diagram of the nth symbol-level correlator group 90n, suitable for use in a non-terrestrial network (NTN) communication system, according to a preferred embodiment of the present invention. Referring to Figure 10, the nth symbol-level correlator group 90n includes a plurality of correlation evaluation units 1000, wherein each correlation evaluation unit 1000 includes a first multiplication circuit 1001, a conjugate circuit 1002, a second multiplication circuit 1003, a first shift register group 1004, a first summator 1005, an absolute value squarer 1006, a second shift register group 1007, and a second summator 1008.

[0093] The first input terminal of the first multiplication circuit 1001 of the first correlation evaluation unit 1000 receives a frequency offset signal with candidate values ​​of residual frequency error. The first input terminal of the first multiplication circuit 1001 of the second correlation evaluation unit 1000 receives a frequency offset signal with candidate values ​​for residual frequency error. And so on. The second input of the first multiplication circuit 1001 receives the delayed preamble. The input terminal of the conjugate circuit 1002 is coupled to the output terminal of the first multiplication circuit 1001, performs a conjugate operation on the output result of the first multiplication circuit 1001, and outputs the result. The first input terminal of the second multiplication circuit 1003 receives the aforementioned received signal. The second input terminal of the second multiplication circuit 1003 is coupled to the output terminal of the conjugate circuit 1002. In this embodiment, the purpose of using the conjugate circuit 1002 is to assume that the received signal... It does indeed contain the delayed preamble corresponding to the user device. This allows us to obtain a measure of the signal strength or energy related to the delayed preamble. This multiplication operation essentially calculates the correlation between the received signal and the delayed preamble, which can be used to extract the presence and location of the delayed preamble. Such multiplication can also provide information about the energy of the delayed preamble in the received signal, because the result of the multiplication is related to the energy and power of the delayed preamble in the received signal to some extent.

[0094] The first shift register group 1004 includes multiple shift registers. The input of the first shift register in the first shift register group 1004 is coupled to the output of the second multiplication circuit 1003, and receives and temporarily stores the output of the second multiplication circuit 1003 at each clock cycle. The first summator 1005 includes multiple inputs and one output. Each input of the first summator 1005 is coupled to the output of each shift register in the first shift register group 1004, for calculating the sum of the outputs of each shift register in the first shift register group 1004. In this embodiment, since the sampling is N, the number of shift registers in the first shift register group 1004 is at least N, and the first summator 1005 performs a summation calculation every N clock cycles.

[0095] The input of the absolute value square calculator 1006 is coupled to the output of the first summator 1005 to calculate the square of the absolute value of the result output by the first summator 1005. The second shift register group 1007 also includes multiple shift registers; according to the above mathematical formula, the number of shift registers in this second shift register group 1007 must be at least m*g*L=20L. The input of the first shift register in the second shift register group 1007 is coupled to the output of the absolute value square calculator 1006. Each input of the second summator 1008 is coupled to the output of each shift register in the second shift register group 1007 to calculate the sum of the outputs of each shift register in the second shift register group 1007, which serves as the similarity measure XNC. For example, the output of the second summator 1008 of the first correlation evaluation unit 1000 corresponds to n delay times, and the residual frequency error is... Similarity measurement The second summator 1008 of the second correlation evaluation unit 1000 outputs the corresponding n delay times, and the residual frequency error is... Similarity measurement ...and so on.

[0096] However, as can be seen from the above embodiments, the hardware required for this implementation is quite large. For example, each narrowband Physical Random Access Channel (NPRACH) preamble in a typical narrowband IoT application has 48 possible frequencies and 14 possible times. Therefore, the aforementioned correlation evaluation unit 1000 must have at least [number missing]. These circuits also need to include integrated circuits such as shift registers, which cannot be simplified in terms of area, making the integrated circuits very large and computationally intensive. Therefore, the following embodiment proposes a relatively simplified implementation circuit.

[0097] Figure 11 illustrates a circuit block diagram of a detection and estimation unit 603 suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention. Referring to Figure 11, in this embodiment, the detection and estimation unit 603 includes a plurality of delay units 1101 and a plurality of omni-RACH correlator groups 1102. The input of the first delay unit 1101 receives the received signal. The output of the first delay unit 1101 is coupled to the input of the second delay unit 1101; the output of the second delay unit 1101 is coupled to the input of the third delay unit 1101, and so on. The input of the first full random access channel correlator group 1102 receives the aforementioned received signal. The input of the second full random access channel correlator group 1102 is coupled to the output of the first delay unit 1101; the input of the third full random access channel correlator group 1102 is coupled to the output of the second delay unit 1101; and so on.

[0098] Comparing the above embodiments with the embodiment in Figure 8, it can be seen that this embodiment is for receiving signals. Perform a time delay, rather than a preamble. A time delay is applied. Furthermore, in this embodiment, each omni-RACH correlator group 1102 can output similarity measurements for different user devices at a fixed delay, corresponding to different residual frequency errors. ~ , ~ … ~ .

[0099] Figure 12 illustrates a circuit block diagram of an omni-RACH correlator group 1102 of a detection and estimation unit 603 suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention. Referring to Figure 12, in this embodiment, the omni-RACH correlator group 1102 is exemplified as the nth omni-RACH correlator group 1102. This omni-RACH correlator group 1102 includes a frequency shifter 1201, a low-pass filter 1202, a downsampling unit 1203, a serial-to-parallel conversion unit 1204, a frequency domain upsampling unit 1205, a frequency hopping de-unit 1206, and a squared and cumulative similarity calculation unit 1207.

[0100] In this embodiment, the input terminal of the frequency shifter 1201 is coupled to the output terminal of the nth delay unit, that is, to receive the received signal delayed by n units of time. This is used to shift the frequency of the delayed received signal to the baseband. In this embodiment, the received signal can be... ride Next, by using the low-pass filter 1202 to remove the high-frequency components, the delayed received signal can be retrieved. Frequency shifted to fundamental frequency to obtain In this embodiment, the low-pass filter 1202 can be a first-order infinite-impulse response (IIR) low-pass filter 1202, and its transfer function can be expressed as follows:

[0101] in, ,in, This indicates the cutoff frequency. The first-order infinite impulse response low-pass filter 802 described above limits its 3dB bandwidth to... .if ,but ,therefore The aforementioned first-order infinite impulse response low-pass filter 1202 can withstand high [impact parameters]. The frequency error. In the above transfer function Can be substituted According to the Nyquist sampling theorem, the output stream data of the first-order infinite impulse response low-pass filter 1202 can be downsampled by a factor of MD = 8 without spectral aliasing. The preamble of the narrowband physical random access channel occupies 48 sub-channels, while the entire LTE band can accommodate N = 512 sub-channels. Therefore, MD = 8 is chosen. This reduces the computational complexity of subsequent operations. A symbol element now contains 64 samples instead of 512. (samples), and there is no information loss or waveform distortion.

[0102] Therefore, in this embodiment, the input terminal of the downsampling unit 1203 is coupled to the output terminal of the low-pass filter 1202 to downsample the signal from the low-pass filter 1202 to obtain... The sampled streaming data. The input of the serial-to-parallel conversion unit 1204 is coupled to the output of the downsampling unit 1203 to convert the serial-to-parallel data into parallel data. The data streams are arranged for parallel output. One output.

[0103] Next, to improve the accuracy of residual frequency error estimation, a frequency domain upsampling method was adopted, dividing each sub-channel into Mu levels, where Mu represents the frequency domain upsampling factor. Frequency domain upsampling is achieved by zero-padding the time-domain downsampled sequence, and then applying the resulting zero-padding sequence to... Point-wise Fast Fourier Transform (FFT). Therefore, in this embodiment, the frequency domain upsampling unit 1205 is... The implementation of the input Fast Fourier Transform circuit includes... One input terminal and multiple output terminals, among which the frequency domain upsampling unit 1205 has a front end. Each input terminal is coupled to the serial-to-parallel conversion unit 1204. One output terminal, and the remaining input terminals are zero-padding. The output terminal of the frequency domain upsampling unit 1205 is configured as an output. The result of the point Fourier transform.

[0104] The de-frequency hopping unit 1206 is coupled to multiple output terminals of the frequency upsampling unit 1205. In this embodiment, the de-frequency hopping unit 1206 includes the frequency hopping mode of each user equipment. Therefore, it can sequentially move the spectrum according to the frequency hopping mode of the user equipment, thereby eliminating the frequency hopping spectrum and its surrounding residual frequency errors. ~ The frequency hopping unit 1206 extracts and outputs the spectral bins of all 48 user equipments at once. Since the frequency hopping unit 1206 can extract and arrange the spectral bins corresponding to all 48 user equipments at once, and all user equipments use the same fast Fourier transform circuit instead of a correlator, this embodiment can significantly reduce the computational load. Then, the square and cumulative similarity measurement calculation unit 1207 calculates the similarity measurement of various residual frequency error candidate values ​​corresponding to a specific user equipment based on the spectral bins output by the multiple outputs of the frequency hopping unit 1206, and outputs it to the multiple outputs of the square and cumulative similarity measurement calculation unit.

[0105] Please compare the embodiments in Figures 8-10 and Figures 11-12. If the single random access channel (mono-RACH) similarity measurement method of Figures 8-10 is implemented, with a sampling rate of N samples per symbol and a sampling period of [missing information]. Please explain. The computational cost of performing the above symbol level correlation (SLC) operation is... A complex multiplier. Thus, the computational complexity of the single random access channel (mono-RACH) similarity measurement for Figures 8-10 can be expressed as: A complex multiplier. However, in the embodiments shown in Figures 11 and 12, the sampling rate... And the 2-basis-fast Fourier transform algorithm (Radix-2 FFT) is used to estimate, and assumes The computational complexity can be expressed as ) complex multipliers, of which the added This represents the computational complexity of the frequency shifter and low-pass filter. Based on the above estimation, those skilled in the art will recognize that the preferred embodiments of Figures 11 and 12 of the present invention can significantly reduce the computational complexity, especially... The higher the value, the greater the difference in computational load.

[0106] The above is just a simple explanation using the number of samples; a more detailed calculation is shown in Table 5 below: mono-RACH SLC omn​​i-RACH SLC Frequency Shift and IIR LPF square magnitude +2N Number of RFE candidates Number of RTE candidates Number of UE Example 1 559650 11200 Example 2 2152500 16128 Table 5

[0107] In Table 5, the Example 1 column uses the following parameters: N = 512, L = 16, RFE [α∆f, β∆f], RTE [0, γT], MD = 8, Mu = 2, N RFE = (β - α) · Mu + 1, N RTE = 2γ + 1, N UE = 6; the Example 2 column uses the following parameters: N = 512, L = 16, RFE [α∆f, β∆f], RTE [0, γT], MD = 8, Mu = 4, N RFE = (β - α) · Mu + 1, N RTE = 2γ + 1, N UE = 12, where, as described in the above examples, β = -α = 33, γ = 5. According to Table 5 above, the actual number of complex multipliers is calculated by adding parameters such as candidate values ​​for residual frequency error (RFE), candidate values ​​for residual time error (RTE), and the number of user devices in sequence. The difference in computational complexity becomes increasingly apparent.

[0108] Although the preferred embodiments in Figures 11 and 12 above are exemplified by hardware implementation, those skilled in the art should understand that with advancements in hardware devices, the preferred embodiments in Figures 11 and 12 are also highly likely to be implemented using software. Therefore, this invention is not limited to the preferred embodiments in Figures 11 and 12 above.

[0109] Figure 13 illustrates a simulated environment for similarity measurement of a communication system suitable for non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention. Referring to Figure 13, in this embodiment, there are six active user equipment UE1, UE2, UE5, UE6, UE9, and UE10.

[0110] The parameter settings used here are as follows: In the frequency domain, a 180 kHz Long Term Evolution Advanced (LTE-A) physical resource block (PRB) is allocated for uplink transmission of Narrowband Internet of Things (NB-IoT). The subcarrier spacing used is ∆f = 3.75 kHz. Therefore, this 180 kHz NB-IoT band can accommodate 48 NB-IoT sub-channels. These 48 NB-IoT sub-channels are divided into 4 groups, each containing 12 subcarriers to accommodate up to 12 User Equipments (UEs). The NB-IoT uplink occupies a guard band of one LTE band. Specifically, 24 sub-channels are located in the upper guard band, and another 24 sub-channels are located in the lower guard band. A narrowband Physical Random Access Channel (NPRACH) preamble consists of four symbol groups (SGs), each composed of five symbols and one cyclic prefix (CP). Therefore, the symbol duration and the cyclic prefix (CP) length are respectively... 266.67 µs and T / 4 = 66.67 µs. The duration of one symbol consists of N = 512 samples.

[0111] Please refer to Figure 7. This simulated scenario assumes only User Equipment 9 (UE 9) is active, and its Residual Frequency Error (RFE) is: The residual time error (RTE) is After passing through an infinite impulse response low-pass filter (IIR LPF), the following was performed: The sample is reduced and then zero-padding is performed to form a sample. A sequence of sample / symbol rates. The resulting sequence is input to... The point is in a Fast Fourier Transform (FFT) unit. Then the FFT output is fed into the frequency hopping unit. In Figure 7, the frequency domain upsampling factor... Figure 14 illustrates a simulation diagram of similarity measurement suitable for non-terrestrial network (NTN) communication systems according to a preferred embodiment of the present invention. Referring to Figure 14, in this embodiment, the setup environment is the same as in the embodiment described in Figure 7 above, but the frequency domain upsampling factor is... Those with ordinary knowledge in the relevant technical field can see that even with the frequency domain upsampling factor... Increasing the sampling factor to 16 does indeed improve data density. Similarly, increasing the sampling factor... Sampling factor The design can be tailored to different environments and precision requirements, therefore, this invention is not limited thereto.

[0112] Table 6 uses an environment with six active user equipment UE1, UE2, UE5, UE6, UE9, and UE10, as shown in Figure 13, to estimate the elevation angle, slant range, Doppler frequency, pre-frequency time-domain compensation, post-frequency time-domain compensation, residual frequency error obtained from estimation similarity measurement, and residual time error, etc., through a communication method / system suitable for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention. UE 1 UE 2 UE 5 UE6 UE9 UE 10 RFE (Δf) 1.1705 0.8285 0.4400 -0.0830 -0.5590 -1.1705 RTE (T) 5.3217 4.2173 3.1302 2.0631 1.0186 0.0000 Elevation Angle 30.00° 31.4280° 32.9828° 34.6794° 36.5349° 38.5679° Slant Range (km) 1075.0880 1030.9101 987.4295 944.7428 902.9623 862.2198 Doppler Frequency (kHz) 43.6274 42.9862 42.2576 41.4271 40.4774 39.3880 Pre-∕postcompensation (kHz) 41.5077 41.5077 41.5077 41.5077 41.5077 41.5077 Estimation Error (kHz) 4-0.15 4-0.15 +0.15 -0.15 -0.15 -0.15 RFE (kHz) 4.3895 3.1070 1.6499 -0.3111 -2.2107 -4.3895 Propagation Delay (ms) 3.5836 3.4364 3.2914 3.1491 3.0099 2.8741 Pre-TA (ms) 2.8741 2.8741 2.8741 2.8741 2.8741 2.8741 Excess Time Delay (μs) 709.5606 562.3007 417.3657 275.0764 135.8081 0.0000 RTE (μs) 1419.1212 1124.6012 834.7314 550.1628 271.6162 0.0000 Table 6

[0113] Figure 15 illustrates a flowchart of pre-compensation and post-compensation in a preferred embodiment of a communication method suitable for non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention. Referring to Figure 15, this pre-compensation and post-compensation in the communication method suitable for non-terrestrial networks (NTNs) primarily aims to ensure that user equipment in the serving cell receives the primary synchronization signal within a specified time and receives random access requests from user equipment within the serving cell. This method includes the following steps:

[0114] Step S1501: Begin.

[0115] Step S1502: Before broadcasting a primary synchronization signal, acquire a frequency domain compensation parameter and a time domain compensation parameter that are pre-calculated and pre-stored by system parameters. The frequency domain compensation parameter and the time domain compensation parameter can be calculated using parameters such as elevation angle and satellite altitude, and then stored in the communication base station. The communication base station can then use these parameters directly without further calculation.

[0116] Step S1503: Broadcast the aforementioned primary synchronization signal in a pre-compensated frequency band and a pre-compensated time. Since the primary synchronization signal is defined in the 3GPP specification as being broadcast in a preset frequency band and within a preset time (such as the fixed sub-frame in the above embodiment), in addition to the frequency needing adjustment according to the frequency domain compensation parameters, the broadcast time of the primary synchronization signal also needs to be adjusted forward so that user equipment within the served cell can receive the aforementioned primary synchronization signal in the specified sub-frame.

[0117] Step S1504: After broadcasting the main synchronization signal, a receive signal is received in a post-compensation frequency band and a post-compensation time. Generally, after receiving the main synchronization signal, the user equipment will send a random access request in the next sub-frame. These signals are subject to propagation delay and frequency shift due to the Doppler effect. Therefore, the communication base station must not only delay the opening time of the receive window but also adjust the receiving frequency to reliably receive signals from the user equipment on the ground.

[0118] Step S1505: End.

[0119] Figure 16 illustrates a flowchart of a user equipment identification method suitable for non-terrestrial network (NTN) communication according to a preferred embodiment of the present invention. Referring to Figure 16, the steps of this user equipment identification method suitable for non-terrestrial network (NTN) communication include:

[0120] Step S1601: Begin.

[0121] Step S1602: Receive a receiving signal .

[0122] Step S1603: Perform two-dimensional correlation function calculation on a majority of user equipments, and obtain a majority of candidate values ​​for residual frequency error and a majority of candidate values ​​for residual time error for each user equipment. Due to the characteristics of non-terrestrial networks, both frequency and time can experience undesirable effects, especially in narrowband communications such as Narrowband Internet of Things (NB-IoT), where signal frequencies can shift to other channels. Therefore, this step performs correlation calculations for residual time and residual frequency errors. This allows the system to determine whether a user device is connected, and to identify the connected frequency and its corresponding time shift, even with frequency and time shifts.

[0123] Step S1604: Determine whether the number of similarity measurements corresponding to a user device exceeds a threshold value. If the determination is yes, proceed to step S1505. If the determination is no, proceed to step S1506.

[0124] Step S1605: Send a response to the user equipment. For example, send a random access response. Additionally, when sending the response to the user equipment, its frequency offset and time offset can also be sent to the user equipment, allowing the user equipment to perform communication corrections using the aforementioned frequency and time offsets, thereby improving subsequent communication quality.

[0125] Step S1606: Do not send a response to the user equipment. Then return to step S1604 to continue the judgment until the judgment of each user equipment is completed.

[0126] Figure 17 illustrates a sub-step flowchart of step S1603 in a communication method suitable for non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention for identifying a user equipment. Referring to Figure 17, step S1603 in this communication method suitable for non-terrestrial networks (NTNs) for identifying a user equipment includes the following steps:

[0127] Step S1701: Based on a specific preamble of a specific user equipment, and according to the residual frequency error and residual time error, perform a symbol-level correlation analysis on the received signal to obtain multiple symbol-level correlation results. For example, as in the above embodiment, each preamble and the received signal are subjected to the above two-dimensional correlation operation. In order to calculate the residual time error and residual frequency error, each preamble also needs to be individually delayed, such as... The above 'n' is the residual time error factor (RTE index), and the above delayed preamble... The carrier wave also needs to be multiplied by the residual frequency error. , where M is the factor of residual frequency error.

[0128] Step S1702: Perform a squared summation similarity measurement on the above multiple symbol-level correlation results to obtain the similarity measure for a specific user device. Using the intuitive method described above, which is similar to the mathematical derivation concept, multiple similarity measures corresponding to each user device can be calculated. .

[0129] While the above method is a more intuitive implementation compared to the mathematical derivation, its only drawback is that the amount of computation is too large.

[0130] Figure 18 illustrates a sub-step flowchart of step S1603 in a communication method suitable for non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention for identifying a user equipment. Referring to Figure 18, step S1603 in this communication method suitable for non-terrestrial networks (NTNs) for identifying a user equipment includes the following steps:

[0131] Step S1801: For the received signal Perform multiple time delay operations to obtain multiple delayed received signals. The above 'n' is the residual time error factor (RTE index).

[0132] Step S1802: For the received signal and the aforementioned plurality of delayed received signals, perform a baseband translation and a time-domain downsampling to obtain a plurality of downsampled symbols. As described in the above embodiment, time-domain downsampling can effectively reduce the complexity of subsequent calculations.

[0133] Step S1803: Perform a time-domain to frequency-domain upsampling conversion on the above-mentioned plurality of downsampled symbols to obtain the frequency upsampled spectrum. This step can be implemented, for example, by using a Fast Fourier Transform unit with a higher sampling rate than the above-mentioned number of sampling points to zero-padding the remaining input, thereby obtaining the frequency upsampled spectrum.

[0134] Step S1804: Based on a frequency hopping mode and residual frequency error assigned to a specific user equipment, the aforementioned frequency upsampling spectrum is circularly shifted to obtain a plurality of spectrum bins corresponding to that specific user equipment. During the circular shift, the peripheral residual frequency error can be captured. ~ Spectral bins.

[0135] Step S1805: Based on the aforementioned plurality of spectral intervals corresponding to a specific user device, calculate a plurality of similarity measures corresponding to the specific user device under different candidate values ​​of residual frequency error. Thus, the similarity measure corresponding to each residual frequency error of factor n of the residual time error can be obtained.

[0136] By improving step S1603 in the above embodiments, the computational complexity can be greatly reduced, and even the overall area of ​​the implemented circuit can be reduced, while achieving the same effect.

[0137] In summary, the preferred embodiments of the present invention, which propose pre-compensation and post-compensation in the frequency and time domains, can reliably enable non-terrestrial network communication base stations to receive random access requests from terrestrial user equipment without altering the specifications of the user equipment. In another preferred embodiment, by performing two-dimensional similarity calculations on a plurality of residual frequency error candidate values ​​and a plurality of residual time error candidate values ​​for each user equipment, the communication base station can correctly identify active user equipment, thereby increasing the success rate of random access requests from user equipment. Furthermore, the two-dimensional similarity calculations in the preferred embodiments of the present invention can also obtain residual frequency error values ​​and residual time error values. The communication base station can also transmit these residual frequency error values ​​and residual time error values ​​to each corresponding active user equipment, thereby allowing user equipment to improve the quality of communication suitable for non-terrestrial networks (NTNs) through its own calculations.

[0138] The specific embodiments described in the detailed description of the preferred embodiments are only used to facilitate the illustration of the technical content of the present invention, and are not intended to narrowly limit the present invention to the above embodiments. All variations and implementations made without departing from the spirit of the present invention and the scope of the appended claims are within the scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0139] 101: Communication Base Station UE0, UE1: User equipment within the service area PSS: Primary Synchronization Signal 501: Time-domain operation diagram of a non-terrestrial network according to a preferred embodiment of the present invention 502:3GPP Terrestrial Network Time-Domain Operation Diagram 503: Time-domain operation diagram of a non-terrestrial network communication base station according to a preferred embodiment of the present invention Tx: Actual Transmitted Subframe Rx: Actual received subframe on-time: Standard Specification Message Box NPSS: Narrowband Primary Synchronization Signal NPRACH0, NPRACH1, NPRACH2: Narrowband Physical Random Access Path (NPRACH) preambles Post-TD: Post-compensation delay time Pre-TA: Advance compensation time RAO: Receive Window for Random Access Opportunities eNB: Ground base station 601: Communication Base Station 602: Service Area 603: Detection and Estimation Unit 604: Dedicated Channel Transmission Unit 801: Mono-RACH Similarity Calculation Unit 900, 901, 902~90n: Symbol-level correlator bank 1000: Correlation Assessment Unit 1001: First Multiplication Circuit 1002: Conjugate Circuit 1003: Second Multiplication Circuit 1004: First shift register group 1005: The First Summation Calculator 1006: Absolute Value Square Calculator 1007: Second shift register group 1008: Second Summation Calculator 1101: Delay Unit 1102: Omni-RACH Correlator Set 1201: Frequency shifter 1202: Low-pass filter 1203: Downsampling unit 1204: Serial-to-Parallel Unit 1205: Frequency Domain Upsampling Unit 1206: Frequency hopping de-activation unit 1207: Unit for calculating squared and cumulative similarity UE1, UE2, UE5, UE6, UE9, UE10: User equipment in an active state. S1501~S1505: Flowchart of a preferred embodiment of the communication method of the present invention S1601~S1606: Flow steps for identifying user equipment in a preferred embodiment of the present invention for a communication method suitable for non-terrestrial networks (NTN). S1701~S1702: Sub-steps of step S1603 in a preferred embodiment of the present invention for identifying user equipment in a communication method suitable for non-terrestrial networks (NTN). S1801~S1702: Sub-steps of step S1603 in a preferred embodiment of the present invention for identifying user equipment in a communication method suitable for non-terrestrial networks (NTN).

Claims

1. A communication system, comprising: A communication base station includes: a detection and estimation unit for receiving a received signal, configured to perform a two-dimensional correlation function calculation on a plurality of user equipments, and obtain a plurality of residual frequency error candidate values ​​and a plurality of similarity measurements of a plurality of residual time error candidate values ​​for each user equipment, and determine whether the user equipment is in an active state based on whether the plurality of similarity measurements corresponding to a user equipment exceeds a threshold value; and a dedicated channel transmission unit for communicating with the detection and estimation unit, configured to transmit a response to the user equipment deemed to be in an active state.

2. The communication system described in item 1 of the request, wherein: When the maximum value exists among multiple similarity measurements corresponding to a specific user device considered to be in an active state, the detection and estimation unit performs peak search on the residual frequency error and the residual time error candidate values ​​of the similarity measurements to obtain a residual frequency error estimate and a residual time error estimate corresponding to the specific user device; and the dedicated channel transmission unit transmits the residual frequency error estimate and the residual time error estimate to the corresponding specific user device considered to be in an active state through a dedicated channel to adjust the frequency and time.

3. The communication system as described in item 1 of the request, wherein, The communication base station further includes: a compensation unit for transmitting a communication beam to the Earth's surface, wherein the communication beam covers a specific service area; wherein, before the communication base station broadcasts a major synchronization signal, the compensation unit acquires frequency domain compensation parameters and time domain compensation parameters pre-calculated and pre-stored by system parameters; wherein, after the major synchronization signal is broadcast, the communication base station receives the received signal in a post-compensation frequency band and at a post-compensation time, wherein the post-compensation frequency band is obtained by adjusting the frequency domain compensation parameters from a first preset frequency band in a specification, and wherein the post-compensation time is obtained by adjusting the time domain compensation parameters from a first preset time in the specification, thereby compensating for frequency offset and time delay.

4. The communication system described in item 3 of the request, wherein, The primary synchronization signal is defined in the specification as being broadcast on a second preset frequency band and within a second preset time period. The communication base station broadcasts the primary synchronization signal in a pre-compensation frequency band and for a pre-compensation time. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using frequency domain compensation parameters, and the pre-compensation time is adjusted from the second preset time to the pre-compensation time using time domain compensation parameters.

5. The communication system as described in item 1 of the request, wherein, The detection and estimation unit includes: a plurality of single random access channel (mono-RACH) similarity measurement calculation units, wherein each of the single random access channel similarity measurement calculation units includes: a plurality of symbol-level correlator banks, wherein each of the symbol-level correlator banks includes a first input terminal, a second input terminal, and multiple output terminals, wherein the first input terminal of each of the symbol-level correlator banks receives a received signal, the second input terminal of the J-th symbol-level correlator bank receives a preamble signal corresponding to the user equipment and delays it by (J-1) time units, and the multiple output terminals of the J-th symbol-level correlator bank respectively output the similarity measurement of the corresponding user equipment under various residual frequency error (RFE) candidate values ​​with a delay of J-1 time units, where J is a natural number representing the index of the symbol-level correlator banks, and J is less than or equal to the total number of the symbol-level correlator banks and the total number of the residual time error candidate values.

6. The communication system as described in item 5 of the request, wherein, Each of these symbol-level correlator groups includes: a plurality of correlation evaluation units, wherein each correlation evaluation unit includes: a first multiplication circuit, including a first input, a second input, and an output, wherein the first input of the first multiplication circuit of each of these correlation evaluation units receives a frequency offset signal with a candidate value of residual frequency error, and the second input of the first multiplication circuit of the I-th single random access channel calculation unit of the J-th symbol-level correlator group receives a preamble signal corresponding to the user equipment and delays it by (J-1) time units. A first multiplication circuit includes an input terminal and an output terminal, wherein the input terminal of the first multiplication circuit is coupled to the output terminal of the first multiplication circuit, and is configured to perform a conjugate operation on the output result of the first multiplication circuit and output the result; a second multiplication circuit includes a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the second multiplication circuit receives the received signal, and the second input terminal of the second multiplication circuit is coupled to the output terminal of the first multiplication circuit; a first shift register group includes a plurality of shift registers, wherein the first shift register group includes a plurality of shift registers. The input of the first shift register in the register group is coupled to the output of the second multiplication circuit; a first summator includes a plurality of inputs and an output, wherein each input of the first summator is coupled to the output of each shift register in the first shift register group, configured to calculate the sum of the outputs of each shift register in the first shift register group; an absolute value square calculator includes an input and an output, wherein the input of the absolute value square calculator is coupled to the output of the first summator, configured to calculate the sum of the outputs of each shift register in the first shift register group; The system is configured to calculate the square of the absolute value output from the first summator; a second shift register group, including multiple shift registers, wherein the input of the first shift register in the second shift register group is coupled to the output of the absolute value square calculator; and a second summator, including a plurality of inputs and an output, wherein each of the inputs of the second summator is coupled to the output of each shift register in the second shift register group, and configured to calculate the sum of the outputs of each shift register in the second shift register group, wherein the second summator of each of the correlation evaluation units outputs multiple similarity measures corresponding to the residual frequency error candidate value and the delay (J-1) residual time error candidate values ​​of the first active user equipment in the J-th symbol level correlator group of the I-th single random access channel calculation unit.

7. The communication system as described in item 2 of the request, wherein, The detection and estimation unit includes: a plurality of delay units, each of which includes an input and an output, wherein the input of the first delay unit receives the received signal, and the output of the Pth delay unit is coupled to the input of the (P+1)th delay unit; and a plurality of omni-RACH correlator groups, each of which includes an input and a plurality of outputs, wherein the input of the Qth omni-RACH correlator group is coupled to the output of the (Q-1)th delay unit, and the input of the first omni-RACH correlator group receives the received signal, wherein the Qth omni-RACH correlator group outputs multiple similarity measures corresponding to the specific user equipment based on the frequency hopping mode corresponding to the specific user equipment and different residual frequency error candidate values ​​corresponding to the specific user equipment, wherein P and Q are natural numbers, and P is greater than 0 and less than the number of delay units, and Q is greater than 1 and less than the number of omni-RACH correlator groups.

8. The communication system as described in item 7 of the request, wherein, Each of these omni-RACH correlator groups includes: a frequency shifter, including an input and an output, wherein the input of the frequency shifter of the Qth omni-RACH correlator group is coupled to the output of the (Q-1)th delay unit, for shifting the received signal to the baseband by a delay of (Q-1) time units; a low-pass filter, including an input and an output, wherein the input of the low-pass filter is coupled to the output of the frequency shifter; a downsampling unit, including an input and an output, wherein the input of the downsampling unit is coupled to the output of the low-pass filter, configured to downsample the signal from the low-pass filter to obtain a data stream sampled at N / MD; and a serial-to-parallel converter, including an input and (N / MD) outputs, wherein the input of the serial-to-parallel converter... A downsampling unit is coupled to the output of the downsampling unit and configured to arrange (N / MD) data streams into one (N / MD) output; a frequency domain upsampling unit includes (N*MU / MD) inputs and a plurality of outputs, wherein the first (N / MD) inputs of the frequency domain upsampling unit are respectively coupled to the (N / MD) outputs of the serial-to-parallel conversion unit, and the remaining inputs of the frequency domain upsampling unit are all set to 0, and the output of the frequency domain upsampling unit is configured to output the result of the (NMU / MD) point Fourier transform; a de-frequency hopping unit includes a plurality of inputs and a plurality of outputs, wherein the plurality of inputs of the de-frequency hopping unit are respectively coupled to a plurality of outputs of the frequency upsampling unit, and the de-frequency hopping unit cyclically moves the spectrum according to the frequency hopping mode allocated to the specific user equipment, and sets the spectrum block corresponding to the specific user equipment (spectral)... The unit outputs spectral bins to multiple output terminals of the frequency hopping de-amplification unit; and a square and cumulative similarity measurement calculation unit, including multiple input terminals and multiple output terminals, wherein the square and cumulative similarity measurement calculation unit calculates the similarity measurement of various residual frequency error candidate values ​​corresponding to a specific user equipment based on the spectral bins output by the multiple output terminals of the frequency hopping de-amplification unit, and outputs it to multiple output terminals of the square and cumulative similarity measurement calculation unit, wherein N, MD, and MU are natural numbers, N represents the number of samples in the symbol duration, MD represents the time-domain downsampling factor, and MU represents the frequency-domain upsampling factor.

9. A communication system, comprising: A communication base station includes: a compensation unit for transmitting a communication beam to the Earth's surface, wherein the communication beam covers a specific service area; wherein, before the communication base station broadcasts a primary synchronization signal, the compensation unit acquires frequency domain compensation parameters and time domain compensation parameters pre-calculated and pre-stored by system parameters; wherein, after the primary synchronization signal is broadcast, the base station receives a received signal in a post-compensation frequency band and at a post-compensation time, wherein the post-compensation frequency band is obtained by adjusting a first preset frequency band in a specification using the frequency domain compensation parameters, and wherein the post-compensation time is obtained by adjusting a first preset time in the specification using the time domain compensation parameters, thereby compensating for frequency offset and time delay.

10. The communication system as described in item 9 of the request, wherein, The primary synchronization signal is defined in the specification as being broadcast on a second preset frequency band and within a second preset time period. The communication base station broadcasts the primary synchronization signal in a pre-compensation frequency band and for a pre-compensation time. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using frequency domain compensation parameters, and the pre-compensation time is adjusted from the second preset time to the pre-compensation time using time domain compensation parameters.

11. The communication system as described in item 10 of the request, wherein, The communication base station includes: a detection and estimation unit for receiving the received signal, configured to perform a two-dimensional correlation function calculation on a plurality of user equipments, and obtain a plurality of residual frequency error candidate values ​​and a plurality of similarity measurements of a plurality of residual time error candidate values ​​for each user equipment, and determine whether the user equipment is in an active state based on whether the plurality of similarity measurements corresponding to a user equipment exceeds a threshold value; and a dedicated channel transmission unit for communicating with the detection and estimation unit, configured to transmit a response to the user equipment deemed to be in an active state.

12. The communication system described in item 11 of the request, wherein: When the maximum value exists among multiple similarity measurements corresponding to a specific user device considered to be in an active state, the detection and estimation unit performs peak search on the residual frequency error and the residual time error candidate values ​​of the similarity measurements to obtain a residual frequency error estimate and a residual time error estimate corresponding to the specific user device; and the dedicated channel transmission unit transmits the residual frequency error estimate and the residual time error estimate to the corresponding specific user device considered to be in an active state through a dedicated channel to adjust the frequency and time.

13. The communication system as described in claim 11, wherein, The detection and estimation unit includes: a plurality of single random access channel (mono-RACH) similarity measurement calculation units, wherein each of the single random access channel similarity measurement calculation units includes: a plurality of symbol-level correlator groups, wherein each of the symbol-level correlator groups includes a first input terminal, a second input terminal, and multiple output terminals, wherein the first input terminal of each of the symbol-level correlator groups receives a received signal, the second input terminal of the Jth symbol-level correlator group receives a preamble signal corresponding to the user equipment and delays it by (J-1) time units, and the multiple output terminals of the Jth symbol-level correlator group respectively output the similarity measurement of the corresponding user equipment under various residual frequency error (RFE) candidate values ​​with a delay of J-1 time units, where J is a natural number, J represents the index of the symbol-level correlator groups, and J is less than or equal to the total number of the symbol-level correlator groups and the total number of the residual time error candidate values.

14. The communication system as described in claim 13, wherein, Each of these symbol-level correlator groups includes: a plurality of correlation evaluation units, wherein each correlation evaluation unit includes: a first multiplication circuit, including a first input, a second input, and an output, wherein the first input of the first multiplication circuit of each of these correlation evaluation units receives a frequency offset signal with a candidate value of residual frequency error, and the second input of the first multiplication circuit of the I-th single random access channel computation unit of the J-th symbol-level correlator group receives a preamble signal corresponding to the user equipment and delays it by (J-1) time units. Unit; a conjugate circuit, including an input terminal and an output terminal, wherein the input terminal of the conjugate circuit is coupled to the output terminal of the first multiplication circuit, configured to perform a conjugate operation on the output result of the first multiplication circuit and output the result; a second multiplication circuit, including a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the second multiplication circuit receives the received signal, and the second input terminal of the second multiplication circuit is coupled to the output terminal of the conjugate circuit; a first shift register group, including a plurality of shift registers, wherein the first shift register group... The input of the first shift register in the first shift register group is coupled to the output of the second multiplication circuit; a first summator includes a plurality of inputs and an output, wherein each input of the first summator is coupled to the output of each shift register in the first shift register group, configured to calculate the sum of the outputs of each shift register in the first shift register group; an absolute value square calculator includes an input and an output, wherein the input of the absolute value square calculator is coupled to the output of the first summator, configured to calculate the sum of the outputs of each shift register in the first shift register group; The system is configured to calculate the square of the absolute value output from the first summator; a second shift register group, including multiple shift registers, wherein the input of the first shift register in the second shift register group is coupled to the output of the absolute value square calculator; and a second summator, including a plurality of inputs and an output, wherein each of the inputs of the second summator is coupled to the output of each shift register in the second shift register group, and configured to calculate the sum of the outputs of each shift register in the second shift register group, wherein the second summator of each of the correlation evaluation units outputs multiple similarity measures corresponding to the residual frequency error candidate value and the delay (J-1) residual time error candidate values ​​of the first active user equipment in the J-th symbol level correlator group of the I-th single random access channel calculation unit.

15. The communication system as described in claim 12, wherein, The detection and estimation unit includes: a plurality of delay units, each of which includes an input and an output, wherein the input of the first delay unit receives the received signal, and the output of the Pth delay unit is coupled to the input of the (P+1)th delay unit; and a plurality of omni-RACH correlator groups, each of which includes an input and a plurality of outputs, wherein the input of the Qth omni-RACH correlator group is coupled to the output of the (Q-1)th delay unit, and the input of the first omni-RACH correlator group receives the received signal, wherein the Qth omni-RACH correlator group outputs multiple similarity measures corresponding to the specific user equipment based on the frequency hopping mode corresponding to the specific user equipment and different residual frequency error candidate values ​​corresponding to the specific user equipment, wherein P and Q are natural numbers, and P is greater than 0 and less than the number of delay units, and Q is greater than 1 and less than the number of omni-RACH correlator groups.

16. The communication system as described in claim 15, wherein, Each of these omni-RACH correlator groups includes: a frequency shifter, including an input and an output, wherein the input of the frequency shifter of the Qth omni-RACH correlator group is coupled to the output of the (Q-1)th delay unit, for shifting the received signal to the baseband by a delay of (Q-1) time units; a low-pass filter, including an input and an output, wherein the input of the low-pass filter is coupled to the output of the frequency shifter; a downsampling unit, including an input and an output, wherein the input of the downsampling unit is coupled to the output of the low-pass filter, configured to downsample the signal from the low-pass filter to obtain a data stream sampled at N / MD; and a serial-to-parallel converter, including an input and (N / MD) outputs, wherein the input of the serial-to-parallel converter... A downsampling unit is coupled to the output of the downsampling unit and configured to arrange (N / MD) data streams into one (N / MD) output; a frequency domain upsampling unit includes (N*MU / MD) inputs and a plurality of outputs, wherein the first (N / MD) inputs of the frequency domain upsampling unit are respectively coupled to the (N / MD) outputs of the serial-to-parallel conversion unit, and the remaining inputs of the frequency domain upsampling unit are all set to 0, and the output of the frequency domain upsampling unit is configured to output the result of the (NMU / MD) point Fourier transform; a de-frequency hopping unit includes a plurality of inputs and a plurality of outputs, wherein the plurality of inputs of the de-frequency hopping unit are respectively coupled to a plurality of outputs of the frequency upsampling unit, and the de-frequency hopping unit cyclically moves the spectrum according to the frequency hopping mode allocated to the specific user equipment, and sets the spectrum block corresponding to the specific user equipment (spectral)... The unit outputs spectral bins to multiple output terminals of the frequency hopping de-amplification unit; and a square and cumulative similarity measurement calculation unit, including multiple input terminals and multiple output terminals, wherein the square and cumulative similarity measurement calculation unit calculates the similarity measurement of various residual frequency error candidate values ​​corresponding to a specific user equipment based on the spectral bins output by the multiple output terminals of the frequency hopping de-amplification unit, and outputs it to multiple output terminals of the square and cumulative similarity measurement calculation unit, wherein N, MD, and MU are natural numbers, N represents the number of samples in the symbol duration, MD represents the time-domain downsampling factor, and MU represents the frequency-domain upsampling factor.

17. A communication method, comprising: Receive a signal; Perform two-dimensional correlation function calculations on a majority of user devices and obtain a majority of residual frequency error candidate values ​​and a majority of residual time error candidate values ​​for each user device; determine whether the user device is active based on whether the majority of similarity measurements corresponding to a user device exceed a threshold value; and send a response to the user device that is considered to be active.

18. The communication method as described in item 17 of the request, wherein, Before receiving the received signal, the method further includes: before a communication base station broadcasts a main synchronization signal, acquiring frequency domain compensation parameters and time domain compensation parameters pre-calculated and pre-stored by system parameters; after the main synchronization signal is broadcast, receiving the received signal in a post-compensation frequency band and a post-compensation time, wherein the post-compensation frequency band is obtained by adjusting the frequency domain compensation parameters from a first preset frequency band in a specification, and the post-compensation time is obtained by adjusting the time domain compensation parameters from a first preset time in the specification, thereby compensating for frequency offset and time delay.

19. The communication method as described in item 18 of the request, wherein, The primary synchronization signal is defined in the specification as being broadcast on a second preset frequency band and within a second preset time period. This includes broadcasting the primary synchronization signal in a pre-compensation frequency band and for a pre-compensation time. The pre-compensation frequency band is adjusted from the second preset frequency band using frequency domain compensation parameters, and the pre-compensation time is adjusted from the second preset time using time domain compensation parameters.

20. The communication method as described in claim 17, wherein, Performing two-dimensional correlation function calculations on the aforementioned plurality of user equipments and obtaining the aforementioned plurality of residual frequency error candidate values ​​and the aforementioned plurality of residual time error candidate values ​​for each user equipment includes: performing a plurality of time delay operations on the received signal to obtain a plurality of delayed received signals; performing a baseband translation and a time-domain downsampling on the received signal and the aforementioned plurality of delayed received signals to obtain a plurality of downsampled symbols; performing a time-domain to frequency-domain upsampling conversion on the aforementioned plurality of downsampled symbols to obtain a frequency upsampled spectrum; performing a circular shift on the aforementioned frequency upsampled spectrum according to a frequency hopping mode and residual frequency error assigned to a specific user equipment to obtain a plurality of spectrum bins corresponding to the specific user equipment; and calculating the similarity measurements corresponding to the specific user equipment under different residual frequency error candidate values ​​based on the aforementioned plurality of spectrum bins corresponding to the specific user equipment.

21. The communication method as described in item 17 of the request, wherein, Performing two-dimensional correlation function calculations on the aforementioned plurality of user equipments and obtaining the aforementioned plurality of residual frequency error candidate values ​​and the aforementioned plurality of residual time error candidate values ​​for each user equipment includes: performing a symbol-level correlation analysis on the received signal based on a specific preamble of a specific user equipment, according to the residual frequency error and the residual time error, to obtain a plurality of symbol-level correlation results; and performing squared cumulative similarity measurement calculations on the aforementioned plurality of symbol-level correlation results to obtain the similarity measurements for the specific user equipment.

22. The communication method as described in item 21 of the request, wherein, Based on a specific preamble of the particular user equipment, and according to the residual frequency error and residual time error, the received signal is subjected to symbol-level correlation analysis to obtain the above-mentioned plurality of symbol-level correlation results, including: performing PxQ symbol-level correlation calculation, wherein the IxJ-th symbol-level correlation calculation includes: multiplying the specific preamble of the I-th time delay of the particular user equipment with the carrier of the J-th residual frequency error to obtain the IxJ-th carrier preamble operation result in each first preset time; multiplying the IxJ-th carrier preamble operation result with the received signal to obtain the IxJ-th received signal carrier preamble result in each first preset time; and accumulating the preset number of received signal carrier preamble results in a preset number of the first preset time to obtain the IxJ-th symbol-level correlation result, wherein P, Q, I, and J are natural numbers, I is greater than 0 and less than P, and J is greater than 0 and less than Q.

23. The communication method as described in item 21 of the request, wherein, The above-mentioned multiple symbol-level correlation results are subjected to squared cumulative similarity measurement calculation to obtain the similarity measurement of the specific user device, including: squaring the absolute value of the IxJth symbol-level correlation result in each second preset time to obtain a squared absolute symbol-level correlation result; and after a second preset number of the second preset time, accumulating a second preset number of squared absolute symbol-level correlation results to obtain the IxJth similarity measurement.

24. A communication method, comprising: Before broadcasting a primary synchronization signal, a frequency domain compensation parameter and a time domain compensation parameter are pre-calculated and pre-stored by system parameters. After the primary synchronization signal is broadcast, a received signal is received in a post-compensation frequency band and a post-compensation time. The post-compensation frequency band is obtained by adjusting the frequency domain compensation parameter from a first preset frequency band in a specification. The post-compensation time is obtained by adjusting the time domain compensation parameter from a first preset time in the specification. This is done to compensate for frequency offset and time delay.

25. The communication method as described in item 24 of the request, wherein, The primary synchronization signal is defined in the specification as being broadcast on a second preset frequency band and within a second preset time period. The communication method further includes broadcasting the primary synchronization signal in a pre-compensation frequency band and a pre-compensation time period. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using a frequency domain compensation parameter, and the pre-compensation time is adjusted from the second preset time to the pre-compensation time using a time domain compensation parameter.

26. The communication methods described in claim 24 further include: Receive the received signal; Perform two-dimensional correlation function calculations on a majority of user devices and obtain a majority of residual frequency error candidate values ​​and a majority of residual time error candidate values ​​for each user device; determine whether the user device is active based on whether the majority of similarity measurements corresponding to a user device exceed a threshold value; and send a response to the user device that is considered to be active.

27. The communication method as described in item 26 of the request, wherein, Performing two-dimensional correlation function calculations on the aforementioned plurality of user equipments and obtaining the aforementioned plurality of residual frequency error candidate values ​​and the aforementioned plurality of residual time error candidate values ​​for each user equipment includes: performing a plurality of time delay operations on the received signal to obtain a plurality of delayed received signals; performing a baseband translation and a time-domain downsampling on the received signal and the aforementioned plurality of delayed received signals to obtain a plurality of downsampled symbols; performing a time-domain to frequency-domain upsampling conversion on the aforementioned plurality of downsampled symbols to obtain a frequency upsampled spectrum; performing a circular shift on the aforementioned frequency upsampled spectrum according to a frequency hopping mode and residual frequency error assigned to a specific user equipment to obtain a plurality of spectrum bins corresponding to the specific user equipment; and calculating the similarity measurements corresponding to the specific user equipment under different residual frequency error candidate values ​​based on the aforementioned plurality of spectrum bins corresponding to the specific user equipment.

28. The communication method as described in item 26 of the request, wherein, Performing two-dimensional correlation function calculations on the aforementioned plurality of user equipments and obtaining the aforementioned plurality of residual frequency error candidate values ​​and the aforementioned plurality of residual time error candidate values ​​for each user equipment includes: performing a symbol-level correlation analysis on the received signal based on a specific preamble of a specific user equipment, according to the residual frequency error and the residual time error, to obtain a plurality of symbol-level correlation results; and performing squared cumulative similarity measurement calculations on the aforementioned plurality of symbol-level correlation results to obtain the similarity measurements for the specific user equipment.

29. The communication method as described in item 28 of the request, wherein, Based on a specific preamble of the particular user equipment, and according to the residual frequency error and residual time error, the received signal is subjected to symbol-level correlation analysis to obtain the above-mentioned plurality of symbol-level correlation results, including: performing PxQ symbol-level correlation calculation, wherein the IxJ-th symbol-level correlation calculation includes: multiplying the specific preamble of the I-th time delay of the particular user equipment with the carrier of the J-th residual frequency error to obtain the IxJ-th carrier preamble operation result in each first preset time; multiplying the IxJ-th carrier preamble operation result with the received signal to obtain the IxJ-th received signal carrier preamble result in each first preset time; and accumulating the preset number of received signal carrier preamble results in a preset number of the first preset time to obtain the IxJ-th symbol-level correlation result, wherein P, Q, I, and J are natural numbers, I is greater than 0 and less than P, and J is greater than 0 and less than Q.

30. The communication method as described in claim 28, wherein, The above-mentioned multiple symbol-level correlation results are subjected to squared cumulative similarity measurement calculation to obtain the similarity measurement of the specific user device, including: squaring the absolute value of the IxJth symbol-level correlation result in each second preset time to obtain a squared absolute symbol-level correlation result; and after a second preset number of the second preset time, accumulating a second preset number of squared absolute symbol-level correlation results to obtain the IxJth similarity measurement.

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