Communication system and communication method

Abstract

The invention provides a communication system and a communication method. The communication method comprises the following steps: obtaining a frequency domain compensation parameter and a time domain compensation parameter in advance through system parameters; and after broadcasting the main synchronization signal, adjusting the original preset frequency band and the preset time through the compensation parameter, and receiving the signal at the base station according to the original preset frequency band and the original preset time so as to compensate for the frequency offset and the time delay. In a better embodiment, the method further comprises the steps of calculating a plurality of similarity metrics, judging whether a specific user equipment in an active state exists according to the similarity metrics, and obtaining a residual frequency error estimation value and a residual time error estimation value corresponding to the specific user equipment through peak value searching. And transmitting the estimated value to the user equipment.

Description

Technical Field

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

[0003] Narrowband IoT, a recently developed framework within the 3G Partner Program specifications, is 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 NPRACH consists of consecutive subcarriers allocated for preamble transmission and is crucial for base stations (BSs) 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 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, for narrowband communication, and for 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 the preferred embodiments of the present invention is to provide a communication system and a communication method that allows a user equipment to modify the communication between the user equipment 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 equipments, and obtain a plurality of candidate values ​​for residual frequency errors and a plurality of similarity measures for the candidate values ​​for residual time errors for each user equipment. Based on whether the plurality of similarity measures corresponding to a user equipment exceed a threshold value, the unit determines whether the user equipment 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 equipment deemed to be in an active state.

[0009] Another preferred embodiment of the present invention provides a communication system including a communication base station for transmitting a communication beam to the Earth's surface, wherein the communication beam covers a specific service area, and includes a compensation unit. Before the communication base station broadcasts a primary synchronization signal, the compensation unit acquires a frequency domain compensation parameter and a time domain compensation parameter 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, 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 large frequency shifts caused by the Doppler effect and long delays caused by long transmission and reception distances.

[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; wherein the communication base station broadcasts the main synchronization signal in a pre-compensation frequency band and a pre-compensation time, wherein 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 wherein 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 comprising: 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 wherein the post-compensation time is obtained by adjusting the time domain compensation parameter from a first preset time in the specification, thereby compensating for large 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. 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 calculations in the embodiments of the present invention 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 the 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. Attached Figure Description

[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 the specification of the invention. 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 The illustration shows a system schematic diagram of a communication system suitable for use in a non-terrestrial network (NTN) according to a preferred embodiment of the present invention.

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

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

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

[0021] Figure 5 The illustration shows a working diagram of "pre-compensation" and "post-compensation" in the time domain, which is suitable for use in a communication system for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention.

[0022] Figure 6 The illustration shows a system schematic diagram of a communication system suitable for use in a non-terrestrial network (NTN) according to a preferred embodiment of the present invention.

[0023] Figure 7 The illustration is 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 The diagram illustrates a functional 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 The diagram illustrates a functional block diagram of a single random access channel (mono-RACH) similarity measurement calculation unit 80u, which is suitable for use in a non-terrestrial network (NTN) communication system according to a preferred embodiment of the present invention.

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

[0027] Figure 11 The diagram illustrates a functional 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 The diagram illustrates a functional 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 The illustration shows a simulated environment suitable for similarity measurement of communication systems for non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention.

[0030] Figure 14 The illustration is 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 The diagram illustrates a pre-compensation and post-compensation flowchart of a communication method suitable for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention.

[0032] Figure 16 The flowchart illustrates a preferred embodiment of the present invention for identifying user equipment in a communication method suitable for non-terrestrial networks (NTN).

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

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

[0035] Symbol explanation:

[0036] 101: Communication base station;

[0037] UE0, UE1: User equipment within the service area;

[0038] PSS: Primary synchronization signal;

[0039] 501: A time-domain operation diagram of a non-terrestrial network according to a preferred embodiment of the present invention;

[0040] 502: Time-domain operation diagram of 3GPP terrestrial networks;

[0041] 503: A time-domain operation diagram of a non-terrestrial network communication base station according to a preferred embodiment of the present invention;

[0042] Tx: Actual transmitted subframe;

[0043] Rx: Actual received subframe;

[0044] on-time: Standard specification frame;

[0045] NPSS: Narrowband primary synchronization signal;

[0046] NPRACH0, NPRACH1, NPRACH2: Narrowband Physical Random Access Channel (NPRACH) preambles;

[0047] Post-TD: The timeframe for post-compensation postponement;

[0048] Pre-TA: Advance compensation time;

[0049] RAO: Receive Window for Random Access Opportunities;

[0050] eNB: Ground base station;

[0051] 601: Communication base station;

[0052] 602: Service Area;

[0053] 603: Detection and estimation unit;

[0054] 604: Dedicated channel transmission unit;

[0055] 801: Multiple Mono-RACH Similarity Calculation Units;

[0056] 900, 901, 902~90n: symbol-level correlator bank;

[0057] 1000: Relevance assessment unit;

[0058] 1001: First multiplication circuit;

[0059] 1002: Conjugate circuit;

[0060] 1003: Second multiplication circuit;

[0061] 1004: First shift register group;

[0062] 1005: The first summation calculator;

[0063] 1006: Absolute Value Square Calculator;

[0064] 1007: Second shift register group;

[0065] 1008: The Second Summation Calculator;

[0066] 1101: Delay unit;

[0067] 1102: Omni-RACH correlator group;

[0068] 1201: Frequency shifter;

[0069] 1202: Low-pass filter;

[0070] 1203: Downsampling unit;

[0071] 1204: Serial-to-parallel conversion unit;

[0072] 1205: Frequency domain upsampling unit;

[0073] 1206: Frequency hopping de-activation unit;

[0074] 1207: Unit for calculating squared and cumulative similarity;

[0075] UE1, UE2, UE5, UE6, UE9, UE10: User equipment that is in an active state;

[0076] S1501~S1505: Flow steps of a preferred embodiment of the communication method of the present invention;

[0077] S1601~S1606: Process steps for identifying user equipment in a preferred embodiment of the present invention suitable for a communication method for non-terrestrial networks (NTN);

[0078] S1701~S1702: Sub-steps of step S1603 of a preferred embodiment of the present invention for identifying user equipment in a communication method suitable for non-terrestrial networks (NTN);

[0079] S1801~S1702: Sub-steps of step S1603 of a preferred embodiment of the present invention for identifying user equipment in a communication method suitable for non-terrestrial networks (NTN). Detailed Implementation

[0080] 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.

[0081] 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 characteristics of NB-IoT help extend device battery life and improve spectrum efficiency, they also lead 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 as the satellite moves rapidly, further exacerbating the impact of ICI and potentially shifting the signal spectrum completely out of the preset receiving frequency band. Furthermore, due to the unavoidable Doppler effect and the long propagation distance of satellites to the ground, 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.

[0082] Non-terrestrial network (NTN) communication systems, especially the current fifth-generation (5G) th Due to the narrowband nature of IoT (Internet of Things) networks, especially the extremely high speed of satellite movement, the relative motion between the signal source (such as a base station on a satellite) and the receiver (such as a ground station or user equipment) causes a severe Doppler effect, resulting in a significant frequency shift and causing the received signal frequency to deviate from the preset receiving frequency. Furthermore, the satellite's altitude is much greater than that of traditional ground base stations, leading to a substantial increase in propagation delay.

[0083] In terrestrial networks, frequency offset allows user equipment using Physical Random Access Channels (PRACHs) to still have a chance to randomly access the communication base station due to the wider channel bandwidth. However, for user equipment using Narrowband IoT Physical Random Access Channels (NPRACHs) in non-terrestrial networks (NTNs), this impact is very severe. Such frequency offset can completely prevent the signals transmitted by narrowband IoT user equipment from accessing the communication base station.

[0084] Furthermore, considering propagation delay, the 3GPP protocol specification stipulates that the base station must send a primary synchronization signal (PSS) at preset intervals. Additionally, user equipment (UE) accurately obtains the cell's synchronization information by receiving the PSS. 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 period, 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 shift, 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.

[0085] Figure 1 The illustration shows a system schematic diagram of a preferred embodiment of the present invention, suitable for use in a non-terrestrial network (NTN). Please refer to... Figure 1 In this embodiment, the communication system suitable for use in non-terrestrial networks (NTN) is based on current fifth-generation (5G) communication technology. th The example is a generation of wireless communication networks, specifically narrowband Internet of Things (NB-IoT). Figure 1 In this communication system, there is a communication base station 101 located on a satellite, and it is assumed that there are two user equipment UE0 and UE1 in the service area of ​​the communication base station 101.

[0086] 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 communication 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, after referring to the embodiments of this invention, should understand 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 primary synchronization signal 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 communication base station 101 needs to broadcast the primary synchronization signal (PSS) at fixed intervals. Furthermore, the user equipment accurately obtains the synchronization information within the service area through the received primary synchronization signal. Within a specified time period (one frame or several time slots) following the transmission of the primary synchronization signal (PSS) by communication base station 101, 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 of the user equipment is also frequency-shifted. Communication base station 101 often fails to receive any signal within the specified receiving window and on the specified frequency band, resulting in random access failure.

[0087] 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, please refer to... Figure 1 In this embodiment, the communication base station 101 is exemplified as a satellite communication base station 101, which transmits a communication beam to the Earth's surface, covering a specific service area within a beam spot. In this embodiment, [the following is used] Figure 1 The working scenarios are shown below, and further analysis is performed based on the parameter settings in Table 1.

[0088]

[0089] Table 1

[0090] Because 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 as follows: Figure 2 As shown. Figure 2 This diagram illustrates a geometrical schematic 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. Please refer to... Figure 2 The observation slant range is calculated based on the elevation angle of the user equipment (UE). According to the auxiliary lines shown in the figure, it can be rearranged into equation (1) using the Pythagorean theorem:

[0091]

[0092] Among them, R E =6.371×10 6 Meter represents the Earth's radius, h sat θ represents the altitude of the serving satellite, 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, which is the time of arrival (ToA), can be calculated: Where C is the speed of light, C = 3 × 10 8 m / s.

[0093] Figure 3 This diagram illustrates the relationship between elevation angle and beam spot size in a preferred embodiment of the present invention, suitable for use in a non-terrestrial network (NTN) communication system. Please refer to... Figure 3 Using the above equation (1) and referring to Figure 3 By applying the cosine theorem iteratively to the beam pattern described in Table 2, 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.

[0094]

[0095] Table 2

[0096] Please refer back to this. Figure 2 ,consider Figure 2 Given the geometric position, we can obtain the following equation:

[0097]

[0098] Equation (2) above can be rearranged into the following equation:

[0099]

[0100] Therefore, θ2 can be explicitly expressed as a function of θ0, and vice versa, as follows:

[0101]

[0102] Therefore, the Doppler frequency is calculated as follows:

[0103]

[0104] in, The instantaneous tangential velocity of the satellite is g = 9.80665 m / s². 2 It is the acceleration due to gravity. f is the maximum Doppler frequency. c Indicates the carrier frequency.

[0105] Using equation (5) above and iteratively applying the cosine theorem, the maximum and minimum Doppler frequencies within the beamspot can be calculated, and the results are listed in Table 3. A common Doppler offset can be calculated from 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 arithmetic mean of the maximum and minimum Doppler frequencies is preset as the common Doppler offset.

[0106]

[0107] Table 3

[0108] For example, Figure 1 When the user equipment is located at the satellite's minimum elevation angle θ0 = 30°, the Earth's radius R E =6.371×10 6 m, satellite altitude h sat =600km=6×10 5 m, satellite velocity V sat =8268.1 m / s. The user equipment speed is extremely low and negligible compared to the satellite's movement speed. Therefore, the Doppler frequency observed by the user equipment is:

[0109]

[0110] When the carrier frequency is f c =2GHz, f D，max =43.64kHz for outbound and inbound traffic, the Doppler frequency doubles to 87.28kHz. Meanwhile, the sub-channel bandwidth of NB-IoT is only 3.75kHz, and a group of 12 sub-channels only occupies 45kHz. This level of Doppler frequency shift causes the signal received by the receiver to be shifted out of the frequency band, making it impossible to be correctly received and detected. 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, for example, on a beam range basis, meaning that all user devices within the same service range receive the same compensation. In this embodiment, the arithmetic mean 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 was calculated in advance), it can obtain the common Doppler frequency experienced by all users within the same beam range.

[0111] For ease of explanation, we will assume the actual Doppler frequency shift of the user equipment (UE) to be X. In other words, after subtracting the common Doppler frequency from the actual Doppler frequency shift, the remaining Doppler frequency shift depends on the location and elevation angle of the user equipment (UE).

[0112] Figure 4 The diagram illustrates the frequency domain pre-compensation and post-compensation processes for downlink and uplink communication between a communication base station and a user equipment according to a preferred embodiment of the present invention. Please refer 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 the 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 specified in the original specification to the aforementioned common Doppler frequency. Here, it is assumed that the communication base station 101 has an error X of a local oscillator. SThe following descriptions all use the downlink reference frequency in the specification as the base frequency. Therefore, the spectral center frequency of the main synchronization signal PSS broadcast by communication base station 101 is... The aforementioned common Doppler frequency The compensation unit, which can be pre-calculated and pre-stored within the communication base station 101, serves as the frequency domain compensation parameter. Therefore, in this case, it is 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 spectrum of the primary synchronization signal (PSS) received by the user equipment is shifted to... The frequency band is the center frequency.

[0113] 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 introduced by the user equipment during alignment is ε. At this point, the user equipment will therefore... This is considered the downlink reference frequency. 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 Δ. dp Therefore, during the random access opportunity (RAO) period, the user equipment... The narrowband physical random access channel (NPRACH) preamble is transmitted to the communication base station 101 at the center frequency.

[0114] Next, the signal containing the preamble is transmitted to the communication base station 101, and is also affected by the Doppler frequency shift. The signal spectrum received by the base station is as follows: The center frequency is used. In this embodiment, the communication base station 101 uses the aforementioned common Doppler frequency. Frequency compensation is performed, meaning that the communication base station 101 will standardize the preset uplink receiving frequency band (X). S +Δ dp Move to The frequency band receives the uplink signal. At this point, the residual frequency error left by the frequency band receiving the signal after the above post-compensation can be expressed as follows:

[0115]

[0116] From the above Figure 4From the derivation and equation (6), it can be seen that the residual frequency error generated during narrowband physical random access channel (NPRACH) reception can be calculated as follows: In NTN, the residual 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 separate compensation at the user end. As can be seen from Table 4, the residual frequency error after applying the "pre-compensation" and "post-compensation" methods proposed in this embodiment is significantly lower than the residual frequency error obtained by prior art through compensation at the user end.

[0117]

[0118] Table 4

[0119] 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 according to the synchronized data. Therefore, the UE does not know whether the received PSS comes from a terrestrial network (TN) base station or a non-terrestrial network (NTN) base station broadcast. Therefore, the frequency domain pre / post-compensation technique used by gNB base stations in non-terrestrial networks (NTNs) maintains backward compatibility with the terrestrial network (TN) specifications in 3GPP.

[0120] Another major challenge of non-terrestrial network communication is high propagation delay. 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 3.58ms and 2.00ms. Such propagation delays are even greater than the length of a preamble symbol (T = 0.2667ms). In order to eliminate propagation delay in non-terrestrial networks (NTN), this embodiment proposes a time-domain "pre-compensation" and "post-compensation" performed in base station 101.

[0121] Figure 5 The diagram illustrates the operation of "pre-compensation" and "post-compensation" in the time domain, suitable for use in a communication system for non-terrestrial networks (NTNs), according to a preferred embodiment of the present invention. Please refer to... Figure 5Reference numeral 501 is a time-domain operation diagram of a non-terrestrial network according to a preferred embodiment of the present invention; reference numeral 502 is a time-domain operation diagram of a 3GPP terrestrial network; reference numeral 503 is a time-domain operation diagram of a communication base station of a non-terrestrial network according to a preferred embodiment of the present invention. In this embodiment, a frame of the downlink signal consists of 10 subframes of 1ms length, and each subframe consists of 2 slots of 0.5ms length, each slot consisting of 7 symbols. The Narrowband Primary Synchronization Signal (NPSS) is located in the sixth subframe and is broadcast once per frame. When the communication base station 101 on the satellite broadcasts the Narrowband Primary Synchronization Signal (NPSS) to all user devices (UEs) within the beam, time advance (Pre-TA) is performed before downlink transmission. Please 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, it can be seen that the narrowband primary synchronization signal (NPSS) needs to be transmitted in the standard specification time sequence on-time. In the actual transmission time sequence Tx, the NPSS transmission is advanced by several subframes. The subframes in which user equipment UE0 and UE1 receive the NPSS are approximately aligned with the standard specification time sequence on-time. In the next subframe after receiving the NPSS, user equipment UE0 and UE1 can transmit the narrowband physical random access channel (NPRACH) preambles NPRACH0 and NPRACH1. Please refer to the standard specification time sequence on-time again; this period constitutes the random access opportunity (RAO). Since user equipment UE0 and UE1 will experience another propagation delay when transmitting the preamble to the satellite, the random access opportunity (RAO) in the communication base station is postponed (Post-TD) in this embodiment, so that when the narrowband physical random access channel (NPRACH) preambles NPRACH0 and NPRACH1 are transmitted to the communication base station, they fall within the postponed receiving window time.

[0122] For ease of explanation in this embodiment, the aforementioned Pre-TA and Post-TD times are, for example, set to a common delay of the same value. In this embodiment, the value of this common delay is 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, the common delay is obtained as shown in Table 2 above. For example, if the relevant parameters of the satellite are currently set to setting 1, the common delay will be set to, for example, 2.00 ms by looking up the table. Figure 5 The invention relates to "pre-compensation" and "post-compensation." While the times (Pre-TA) and (Post-TD) in the above embodiments are set to the same common delay, and this common delay is set to the minimum propagation delay within the beam range, those skilled in the art should understand that the invention does not limit the set 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 also understand that the invention does not limit the set values ​​of the times (Pre-TA) and (Post-TD) to integer multiples of the slot length.

[0123] The random access procedure begins 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 the common delay D. min The PSS received by UE0 and UE1 may be delayed. Each UE performs time and frequency alignment independently, that is, synchronization with the received Narrowband Physical Random Access Path (NPRACH) main 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 treat this subframe as a Random Access Opportunity (RAO).

[0124] 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 D. minThe preambles NPRACH0 and NPRACH1 arrive at the satellite communication base station during the delayed random access opportunity (RAO) reception window.

[0125] Next, as Figure 5 As shown in the lower half, 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 Path (NPRACH) preamble (NPRACH2) back to the ground base station eNB in ​​the next subframe. 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 the common delay D min The pre-TA (Pre-Time Advance) achieved can be considered as a delay in the transmission of the Narrowband Primary Synchronization Signal (NPSS), since the NPSS is broadcast periodically at 10ms intervals, which is the length of a 5G New Radio (NR) frame in Non-Terrestrial Networks (NTNs). Simultaneously, the RAO (Range Objective of the Occurrence) delay should be implemented by delaying the RAO window (10ms + D). min Specifically, for transparent payloads, such as non-terrestrial satellites operating as analog radio frequency repeaters, the propagation delay and Doppler shift 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 method can also be pre-calculated and stored at the ground base station as described above; however, the compensation method will include the time and frequency from the ground base station to the satellite (feeder link) plus the time and frequency from the satellite to the user equipment (service link). Ground base stations possess powerful computing capabilities, real-time ephemeris and beam-satellite geometry information, and high-precision local oscillators, enabling frequency / time and pre / post compensation to be implemented at the base station as described above.

[0126] The above embodiments 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 the signal sent by the user equipment within its service area. Within the same service area, user equipment has different locations and elevation angles; even if the base station implements the aforementioned frequency / time and pre / post-compensation, there will still be different residual frequency and residual time errors between the NPRACH of different users.

[0127] For ease of explanation of this embodiment, the baseband equivalent signal transmitted by the u-th user equipment is represented in discrete time as follows:

[0128]

[0129] Where k represents the time index, kt s t represents the instantaneous time of sampling. s For the sampling period, and T and N represent the symbol length and the number of times each symbol is sampled, respectively. E represents signal power. s The energy of the signal during the sampling time is represented by v[u, l, m]; v[u, l, m] represents the normalized subcarrier frequency used in the m-th symbol group (SG) of the l-th preamble from the u-th user equipment. For simplicity, unless the variables u, l, or m need to be explicitly specified in the expression, v[u, l, m] will be used to represent v[u, l, m] below.

[0130] The superimposed signal received by the base station can be represented as:

[0131]

[0132] in,

[0133]

[0134] w u,k Represents the complex-valued channel gain, ∈ u Indicates the normalized frequency error, l u φ represents the time error occurring in the u-th uplink. u，0 This represents the initial phase error caused by the non-homogeneous frequency reduction process at the front end. For simplicity, we use... Perform power normalization on the above equations. The normalization frequency error in equation (8) ∈ u It is relative to the subchannel bandwidth (also known as subcarrier spacing). The normalized residual frequency error is defined as follows:

[0135] Where, ε u ε represents the residual frequency error of the u-th uplink, in Hertz (Hz). u The calculated values ​​are listed in rows 3 and 6 of Table 4, while the normalized frequency error ∈ u It has also been calculated and listed in rows four and seven of Table 4. n′[k]=n′(kt) s ) represents n′(k) at time kt sThe sampled additive white Gaussian noise (AWGN) has a power spectral density (PSD) of S. n (f) = N0. The zero-to-zero bandwidth of the receiving filter here is... Therefore, the noise n′[k] is a noise with a mean of zero and a variance of . An uncorrelated Gaussian sequence. Due to the normalization relation. n[k] is a subset of k with a mean of zero and a variance of 0. Uncorrelated Gaussian sequences.

[0136] For the u-th user equipment, the received signal in equation (8) above can be rewritten as:

[0137]

[0138] Here, the first term represents the preamble from the u-th user device, which is the desired signal term, and the second term n... ι [k] is then:

[0139] n ι [k] = ι[k] + n[k]

[0140] This expression includes an inter-carrier interference (ICI) term, which is expressed as follows:

[0141]

[0142] n[k] terms represent terms with a mean of zero and a variance of . The additive white Gaussian noise (AWGN) is used. 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 w... u，k and initial phase φ u，0 When considered as a non-demand parameter, ∈ in the u-th uplink u With l u The similarity function and the log-likelihood function can be written in the following forms:

[0143]

[0144] Therefore, it includes the interference parameter w u，k and φ u,0 ,∈ u With l uThe joint maximum-likelihood estimation (JMLE) can be written as:

[0145]

[0146] It is worth noting that in the above equation (12), |w u，k |and This is unrelated to the search for the maximum value. Therefore, the output of the time-domain correlation operation can be represented as follows:

[0147]

[0148] Among them, the residual frequency error estimate and residual time error estimate The frequency error ∈ ∈ (i, u) is estimated to occur in the u-th uplink. u and the time error l occurring in the u-th uplink u .

[0149] Joint Maximum Similarity Estimation (JMLE) aims to find the frequency error ∈ ∈ U-th uplink that occurs when the maximum value is reached. u and the time error l occurring in the u-th uplink u 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.

[0150] 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:

[0151]

[0152] Where m = 0, 1, 2, 3; q = 0, 1, 2, 3, 4.

[0153] in, It is the desired term; I l,m,q Indicates the inter-channel interference (ICI) term; n l,m,q This indicates the noise term. N cp and N SGThese represent the number of samples in the cyclic prefix (CP) and the number of samples in the symbol group, respectively.

[0154] The part requested It can be represented as follows:

[0155]

[0156] Inter-channel interference (ICI) section I l，m，q It can be represented as follows:

[0157]

[0158] For the noise part, we assume it is additive white Gaussian noise (AWGN), and we will ignore the derivation details here.

[0159] Using the above Symbol Rank Correlation (SLC) method, the similarity measure detections on L preambles can be represented as the accumulation of the squared magnitudes of the SLC output, as follows:

[0160]

[0161] in,

[0162]

[0163] By the possible uth user device as well as By inputting the data one by one, you can obtain the two-dimensional similarity measure results. Then, by finding the maximum value among these two-dimensional similarity measure results corresponding to the u-th user device, 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 This is an estimate of the residual frequency error and residual time error for the user. The base station can then issue a random access response to an active user equipment, wherein the random access response includes the estimated values ​​of the residual frequency error and residual time error for the u-th user equipment. and ).

[0164] As mentioned above, Figure 6 The illustration shows a system schematic diagram of a preferred embodiment of the present invention, suitable for use in a non-terrestrial network (NTN). Please refer to... Figure 6 In this embodiment, the communication system suitable for non-terrestrial networks (NTN) is also based on the current fifth generation (5G). th Taking a wireless communication network as an example, specifically a narrowband Internet of Things (NB-IoT), this communication system suitable for non-terrestrial networks (NTN) includes a communication base station 601 and a service area 602. It is assumed that the service area 602 includes a plurality of NB-IoT user devices. The communication base station 601 is also exemplified as a satellite base station. This communication base station 601 includes a detection and estimation unit 603 and a dedicated channel transmission unit 604. Additionally, the communication base station 601 also includes a compensation unit (not shown) to compensate for frequency errors and time delays, as described above. Figure 4 and Figure 5 .

[0165] The communication base station 601 is used to open a receiving window to receive a received signal r[k] within, for example, the 3GPP specification time, or the post-compensation time as described above. The detection and estimation unit 603 receives the received signal r[k] and performs a two-dimensional correlation function calculation for the majority of user equipments that can access the communication base station 601. In the prior art, the communication base station 601 only performs a simple one-time one-dimensional correlation function calculation for the majority of user equipments that can access the network to determine whether the corresponding user equipment has 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 the random access preamble of narrowband IoT undergoes a frequency offset, its spectrum will cross into a non-standard channel. Furthermore, the random access preamble of narrowband IoT experiences a long delay, and its arrival time at the base station is later than the preset reception time. Therefore, simply using the one-dimensional correlation function calculation of the previous technology will not be able to confirm whether the user device is active.

[0166] To extend the estimation range of Residual Timing Error (RTE), the detection and estimation unit 603 of this invention employs a rake structure design, where each arm corresponds to a candidate RTE value. To extend the estimation range of Residual Frequency Error (RFE), each arm in the rake structure design contains a set of Symbol-Level Correlation Operations (SLCs), where each SLC corresponds to a candidate RFE value. Furthermore, the set of SLCs on a branch in the rake structure is implemented using an FFT demodulator. To reduce complexity, this invention employs a time-domain downsampling method. To improve the estimation accuracy of residual frequency error, sufficient zeros are padded to the input sequence of the FFT demodulator (the time-domain downsampled sequence) to achieve frequency-domain upsampling. Therefore, through a grid search method, residual frequency error and residual timing error can be accurately estimated with accuracy finer than the subcarrier spacing and symbol time fractions. Ultimately, this invention enables joint maximum-likelihood estimation of residual frequency and residual time errors simultaneously in both frequency and time dimensions with high precision and extended range. In this embodiment, using the aforementioned two-dimensional correlation function, by performing multiple similarity measurements on multiple candidate values ​​of residual frequency and residual time errors for multiple user devices, the absolute value measurement of the spectral bins of each user device can be obtained; this is the similarity measurement.

[0167] Figure 7 The illustration depicts a simulation diagram of similarity measurement suitable for use in a non-terrestrial network (NTN) communication system, according to a preferred embodiment of the present invention. As described above... Figure 7As shown, the X-axis represents the residual frequency error, the Y-axis represents the residual time error, and the Z-axis represents the similarity measures. If any similarity measure exceeds a predefined threshold, the corresponding user equipment (UE) is considered active. A random access response (RAR) can then be sent to this UE. This significantly reduces the detection miss probability of the communication base station 601 and increases the UE's access success rate. The dedicated channel transmission unit 604 communicates with the detection and estimation unit 603, responsible for transmitting a response, such as a random access response (RAR), to UEs deemed active. When the similarity measures of UEs do not exceed the predefined threshold, the detection and estimation unit 603 determines that the corresponding UE is inactive, and the random access response (RAR) will not be sent.

[0168] 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 residual frequency error candidate values ​​and residual time error candidate values ​​of the aforementioned similarity measures to obtain residual frequency error estimates and residual time error estimates corresponding to the user equipment. At this time, the communication base station 601 can also transmit the aforementioned residual frequency error estimates and residual time error estimates 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 residual frequency error estimates and residual time error estimates, thereby improving communication quality.

[0169] Figure 8 The diagram illustrates a functional 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. Please refer 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, 802, ... 80u. In this embodiment, the first single random access channel (mono-RACH) similarity measurement calculation unit 801 receives the received signal r[k] and the preamble p[k, UE1] corresponding to the first random access channel. Similarly, the u-th single random access channel similarity measurement calculation unit 80u receives the received signal r[k].

[0170] And the preamble p[k, UEu] corresponding to different u-th random access channels. The preamble p[k, UEu] can be regarded as an important basis for determining whether the user equipment is connected. The user equipment will randomly select a preamble from the available preamble set according to a certain random algorithm. Therefore, in this embodiment, the preamble p[k, UEu] is used as the input of the u-th single random access channel (mono-RACH) similarity measurement calculation unit 80u, and the received signal r[k] and the preamble p[k, UEu] are used to perform correlation function calculation, thereby determining whether the u-th user equipment is in an active state.

[0171] Figure 9 The diagram illustrates a functional block diagram of the u-th single random access channel (mono-RACH) similarity calculation unit 801, suitable for use in a non-terrestrial network (NTN) communication system, according to a preferred embodiment of the present invention. Please refer to... Figure 9 The u-th single random access channel similarity measurement calculation unit 801u includes multiple symbol-level correlator banks (SLC banks) 900, 901, 902 to 90n. The first input of each symbol-level correlator bank 900 to 90n receives the received signal r[k]. The second input of the zeroth symbol-level correlator bank 900 receives the undelayed preamble p[k, UEu]. The second input of the first symbol-level correlator bank 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 from 900 to 90n outputs multiple similarity metrics X corresponding to the delay time. NC,u .

[0172] Figure 10 The diagram illustrates a functional 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. Please refer 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 square calculator 1006, a second shift register group 1007, and a second summator 1008.

[0173] The first input terminal of the first multiplication circuit 1001 of the first correlation evaluation unit 1000 receives the frequency offset signal e with the candidate value of the residual frequency error. j2π(-3)Δfk This signal achieves a frequency shift of (-3)Δf. The first input of the first multiplication circuit 1001 of the second correlation evaluation unit 1000 receives the frequency shift complex exponential sequence e with residual frequency error candidate values. j2π(-2.5)Δfk This sequence achieves a frequency offset of (-2.5)Δf. And so on. The second input of the first multiplier circuit 1001 receives the delayed preamble. The input of the conjugate circuit 1002 is coupled to the output of the first multiplication circuit 1001, performing a conjugate operation on the output of the first multiplication circuit 1001 and outputting the result. The first input of the second multiplication circuit 1003 receives the received signal r[k], and the second input of the second multiplication circuit 1003 is coupled to the output of the conjugate circuit 1002. In this embodiment, the purpose of using the conjugate circuit 1002 is to assume that the received signal r[k] does indeed contain the delayed preamble corresponding to the user equipment. This allows us to obtain a measure of the signal strength or energy related to the delayed preamble. This multiplication operation essentially calculates the received signal r[k] and the delayed preamble. The correlation between them can be used to extract the delayed preamble. The presence of the preamble and its location embedded in the received signal r[k]. The received signal r[k] is composed of multiple NPRACH preambles transmitted from different user devices and is subject to various channel impairments and noise interference.

[0174] 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 an output. Each input of the first summator 1005 is coupled to the output of each shift register in the first shift register group 1004 to calculate the sum of the outputs of each shift register in the first shift register group 1004. In this embodiment, since each symbol is sampled N times, 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.

[0175] 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 5, because an NPRACH preamble contains 20 symbols, and the similarity measure is calculated based on L preambles. 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 X. NC For example, for u user equipment (UEu), the second summator 1008 of the first correlation evaluation unit 1000 outputs a similarity measure corresponding to n delay times, with a residual frequency error of (-3)Δf. For u user equipments (UEs), the second summator 1008 of the second correlation evaluation unit 1000 outputs a similarity measurement corresponding to n delay times, with a residual frequency error of (-2.5)Δf. ...and so on.

[0176] 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) in a typical narrowband IoT application has 48 preambles, 14 possible frequency errors, and 10 possible time errors. Therefore, the aforementioned correlation evaluation unit 1000 would require at least 48 × 14 × 10 = 6720 sets. Furthermore, this would need to include integrated circuits such as shift registers, which cannot simplify the area calculation, making the integrated circuits very large and the computational load enormous. Therefore, the following embodiments propose a relatively simplified implementation circuit.

[0177] Figure 11 The diagram illustrates a functional 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. Please refer to... Figure 11In this embodiment, the detection and estimation unit 603 includes a plurality of delay units 1101 and a plurality of fully random access channel correlator banks 1102 (represented in the diagram as Omni-RACH correlator bank 0, Omni-RACH correlator bank 1 to Omni-RACH correlator bank n). The input of the first delay unit 1101 receives the received signal r[k]; 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 Omni-RACH correlator bank 0 1102 receives the received signal r[k]; the input of the second Omni-RACH correlator bank 1 1102 is coupled to the output of the first delay unit 1101; the input of the third Omni-RACH correlator bank 1102 is coupled to the output of the second delay unit 1101; and so on.

[0178] Comparing the above embodiments and Figure 8 As can be seen from the embodiment, this embodiment performs a time delay on the received signal r[k], rather than on the preamble p[k, UEu] of u user equipments. Furthermore, in this embodiment, the first Omni-RACH correlator bank 0 1102 outputs a similarity measure X. NC，：，L [3Δf,0]~X NC，：，L [(-3)Δf,0)] The second fully random access channel correlator bank (Omni-RACH correlator bank 1) outputs a similarity measure. The nth fully random access channel correlator bank (Omni-RACH correlator bank n) outputs a similarity measure. In other words, each omni-RACH correlator group 1102 can output the values ​​of all user devices at a fixed delay. Below, similarity measurement of different residual frequency errors.

[0179] Figure 12The diagram illustrates a functional 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. Please refer 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.

[0180] 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 base frequency. In this embodiment, the spectrum of the random access channel is placed in the sidebands on both sides, which can shift the frequency of the received signal... Multiply by cos(πk) to obtain Next, the high-frequency components are removed by filtering with low-pass filter 1202. In other cases, NPRACH may be placed at (f c In the frequency band where +δΔf is the center frequency, noncoherent demodulation (or noncoherent downconversion) has already processed the carrier frequency f. c This involves lowering the NPRACH spectrum to near the intermediate frequency or fundamental frequency; this part of the work, moving to the fundamental frequency, is then replaced by... Implementation; the aforementioned f c ,t s The values ​​of δ and Δf are defined in the protocol specification. In this embodiment, the low-pass filter 1202 can be a first-order infinite-impulse response (IIR) low-pass filter 1202, whose transfer function can be expressed as follows:

[0181]

[0182] Where, a = exp(-2πf cutoff t s ), where f cutoffThis indicates the cutoff frequency. The first-order infinite impulse response low-pass filter 802 described above limits its 3dB bandwidth to ±f. cutoff If f cutoff =32Δf, then therefore The aforementioned first-order infinite impulse response low-pass filter 1202 can withstand frequency errors as high as ±(32-24)Δf=±8Δf. The 'a' in the aforementioned transfer function can be substituted into... 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 M. D =8 times, without spectral aliasing or information loss. The preamble of a narrowband physical random access channel occupies 48 sub-channels, and the symbols of a narrowband IoT contain N=512 samples. Therefore, choosing... This reduces the computational complexity of subsequent operations. The number of symbols per element has been reduced from 512 to 64. Moreover, there was no information loss or waveform distortion.

[0183] 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. Thus, the downsampling unit 1203 outputs a lower-rate data stream, and its sampling period becomes M. D t s And each symbol is sampled as 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 a single sample. Data from each sampling point is arranged for parallel output. One output.

[0184] Next, to improve the accuracy of residual frequency error estimation, a frequency domain upsampling method was adopted, dividing each sub-channel into M... u Each level, M u This represents the frequency domain upsampling factor. Frequency domain upsampling is achieved through zero padding of the parallel output of the serial-to-parallel unit 1204. The resulting zero-padding sequence is then applied to a Fast Fourier Transform (FFT), with both the input and output points being 1. Therefore, in this embodiment, the frequency domain upsampling unit 1205 is... The implementation of the input Fast Fourier Transform circuit includes... Each input terminal and One output terminal, of which the front of the frequency domain upsampling unit 1205 Each input terminal is coupled to the serial-to-parallel conversion unit 1204. One output terminal, the rest Each input terminal is zero-padding. The output terminal of the frequency domain upsampling unit 1205 is configured as an output. The result of the point Fourier transform.

[0185] The de-frequency hopping unit 1206 is coupled to multiple outputs of the frequency upsampling unit 1205. In this embodiment, the de-frequency hopping unit 1206 internally includes the frequency hopping mode of each user equipment. Therefore, the output (i.e., the spectrum) of the frequency upsampling unit 1205 can be sequentially shifted in the opposite frequency direction according to the frequency hopping mode of the user equipment. Since the frequency hopping mode corresponding to a user equipment has been removed by the de-frequency hopping unit 1206, the spectral bins output by the de-frequency hopping unit 1206 represent the correlation measurement of that user equipment at possible residual frequency error candidate values ​​(ranging from -3Δf to 3Δf). Because the de-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 array, this embodiment can significantly reduce the computational load. Subsequently, the square and cumulative similarity measurement calculation unit 1207 calculates the similarity measurement corresponding to various residual frequency error candidate values ​​for a specific user equipment based on the spectral bins output by the multiple output terminals of the de-frequency hopping unit 1206, and outputs it to the multiple output terminals of the square and cumulative similarity measurement calculation unit.

[0186] Please compare Figures 8-10 Implementation examples and Figures 11-12 In the embodiments, if Figures 8-10 The single random access channel (mono-RACH) similarity measurement is implemented with a sampling rate of N samples per symbol and a sampling period of t. s To clarify, performing the above symbol level correlation (SLC) operation requires 2N complex multipliers. Thus, Figures 8-10 The computational complexity of a single random access channel (mono-RACH) similarity measurement can be represented as 2N complex multipliers. If the system has N UE For each user device that may be powered on, the computational complexity for similarity measurement would be 2N·N. UE N complex multipliers; simultaneously, N UE =48, N=512. However, with Figures 11-12 In an embodiment, the sampling rate And the 2-basis-fast Fourier transform algorithm (Radix-2 FFT) is used to estimate, assuming M u =M D =8, the computational complexity can be expressed as Consider N complex multipliers in the system. UE For a user device that may be powered on, the computational workload for similarity measurement still only requires... A complex multiplier. From the above estimation, it will be apparent to those skilled in the art that the present invention... Figures 11-12 The preferred embodiment can significantly reduce the computational load, especially when the value of N and the downsampling factor M are high. D and the number of user devices N UE The higher the value, the greater the difference in computational load.

[0187] The above is just a simple explanation using the number of samples; a more detailed calculation is shown in Table 5 below:

[0188]

[0189] Table 5

[0190] In Table 5, the Example 1 column uses the following parameters: N = 512, L = 16, RFE range is between [αΔf, βΔf], RTE range is between [0, γT], M D =8,M u =2, N RFE = (β-α)·M u +1, N RTE =2γ+1, N UE =6; Example 2 uses the following parameters: N=512, L=16, RFE range between [αΔf, βΔf], RTE range between [0, γT], M D =8,M u =4, N RFE = (β-α)·M u +1, N RTE =2γ+1, N UE =12, where, as described in the above embodiments, β = -α = 3, γ = 3. According to Table 5 above, the actual number of complex multipliers is calculated by sequentially adding parameters such as the number of candidate values ​​for residual frequency error (RFE), the number of candidate values ​​for residual time error (RTE), and the number of user devices. The difference in computational complexity becomes increasingly apparent.

[0191] The above Figures 11-12 Although the preferred embodiment is illustrated by hardware implementation, those skilled in the art will understand that with advancements in hardware devices, Figures 11-12 The preferred embodiments are also highly likely to be implemented using software. Therefore, the present invention is not limited to the above-described embodiments. Figures 11-12 The preferred embodiments are limited to those described herein.

[0192] Figure 13 The illustration depicts a simulated environment suitable for similarity measurement in a non-terrestrial network (NTN) communication system, according to a preferred embodiment of the present invention. Please refer to... Figure 13 In this embodiment, there are six active user equipment UE1, UE2, UE5, UE6, UE9, and UE10.

[0193] The parameter settings used here are as follows: In the frequency domain, a 180kHz Long Term Evolution Advanced (LTE-A) or 3GPP New Radio (NR) physical resource block (PRB) is allocated for uplink transmission of Narrowband Internet of Things (NB-IoT). The subcarrier spacing used is Δf = 3.75kHz. Therefore, this 180kHz 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 in a LTE-A or 3GPP New Radio (NR) 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... And T / 4 = 66.67 μs. The duration of one symbol consists of N = 512 samples.

[0194] Please refer to Figure 7 This simulation assumes only User Equipment 9 (UE 9) is active, with a residual frequency error (RFE) of -0.5590Δf and a residual time error (RTE) of 1.0186T. After passing through an infinite impulse response low-pass filter (IIR LPF), M... D =8 downsampling, then zero-padding to form a... A sequence of sample / symbol rates. The resulting sequence is input to... The point is then fed into a Fast Fourier Transform (FFT) converter. The FFT converter output is then fed into a frequency hopping de-conversion unit. Figure 7 In the frequency domain, the upsampling factor M u =2. Figure 14 The illustration depicts a simulation diagram of similarity measurement suitable for use in a non-terrestrial network (NTN) communication system, representing a preferred embodiment of the present invention. Please refer to... Figure 14 In this embodiment, the environment is set up as described above. Figure 7 The implementation is the same, however the frequency domain upsampling factor M u =16. Those skilled in the art will recognize that the frequency domain upsampling factor M... u Increasing the sampling factor M to 16 does indeed improve data density; the candidate values ​​for residual frequency error are now 8 times closer together, thus improving the accuracy of residual frequency error estimation. Similarly, increasing the sampling factor M... u Sampling factor M D The design can be tailored to different environments, complexity requirements, and precision requirements; therefore, this invention is not limited thereto.

[0195] Table 6 uses the following example: Figure 13 In an environment with six active user equipment UE1, UE2, UE5, UE6, UE9, and UE10, the elevation angle, slant range, Doppler frequency, and time delay are calculated using a communication method / system suitable for non-terrestrial networks (NTN) according to a preferred embodiment of the present invention. Then, through the aforementioned pre-frequency / time compensation and post-frequency / time compensation, the estimated range of residual frequency error and residual time error required for similarity measurement is calculated.

[0196] UE 1 UE 2 UE 5 UE6 UE9 UE 10 Residual frequency error RFE(Δf) 1.1705 0.8285 0.4400 -0.0830 -0.5590 - Residual time error RTE(T) 5.3217 4.2173 3.1302 2.0631 2.0631 0.0000 Elevation Angle 30.00° 31.4280° 32.9828° 34.6794° 36.5349° 38.5679° Slant Range 1075.0880 1030.9101 987.4295 944.7428 902.9623 862.2198 Doppler frequency 43.6274 42.9862 42.2576 41.4271 40.4774 39.3880 Pre- and post-event frequency compensation 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 Residual frequency error (kHz) 4.3895 3.1070 1.6499 -0.3111 -2.2107 - Transmission delay (ms) 3.5836 3.4364 3.2914 3.1491 3.0099 2.8741 Pre-compensation time (ms) 2.8741 2.8741 2.8741 2.8741 2.8741 2.8741 Timeout delay (μs) 709.5606 562.3007 417.3657 275.0764 135.8081 0.0000 Residual time error (ms) 1419.1212 1124.6012 834.7314 550.1628 271.6162 0.0000

[0197] Table 6

[0198] Figure 15 The diagram illustrates a pre-compensation and post-compensation flowchart suitable for a communication method used in non-terrestrial networks (NTNs) according to a preferred embodiment of the present invention. Please refer to... Figure 15 This pre-compensation and post-compensation method, suitable for communication in non-terrestrial networks (NTNs), aims to ensure that user equipment in the serving cell receives the primary synchronization signal within a specified time and that the communication base station receives random access requests from user equipment within the serving cell. This method includes the following steps:

[0199] Step S1501: Begin.

[0200] Step S1502: Before broadcasting a primary synchronization signal, acquire a frequency domain compensation parameter and a time domain compensation parameter pre-calculated and pre-stored by system parameters. These frequency and time domain compensation parameters can be calculated using, for example, elevation angle and satellite altitude, and then stored in the communication base station. Since the satellite altitude, the tilt angle served by the satellite base station, and the size of the service range are fixed, the communication base station can directly use these parameters without repeated online calculations.

[0201] 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 a fixed subframe 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 primary synchronization signal in the specified subframe.

[0202] Step S1504: After the main synchronization signal is broadcast, a received 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 subframe. 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 receiving window but also adjust the receiving frequency to reliably receive signals from the user equipment on the ground.

[0203] Step S1505: End.

[0204] Figure 16 The diagram illustrates a flowchart of a user equipment identification method suitable for use in a non-terrestrial network (NTN) communication method, according to a preferred embodiment of the present invention. Please refer to... Figure 16 The steps for identifying user equipment suitable for communication methods used in non-terrestrial networks (NTNs) include:

[0205] Step S1601: Begin.

[0206] Step S1602: Receive a received signal r[k].

[0207] 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 similarity measures X for the majority of candidate values ​​for residual time error for each user equipment. NC,u,LDue to the characteristics of non-terrestrial networks, both frequency and time can experience undesirable effects, especially in narrowband communication, 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, even with frequency and time shifts, and to identify the residual frequency and time errors associated with the connection.

[0208] 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 S1605. If the determination is no, proceed to step S1606.

[0209] 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, the estimated residual frequency error and the estimated residual time error can also be sent to the user equipment, allowing the user equipment to correct for these frequency and time errors and improve subsequent communication quality.

[0210] 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.

[0211] Figure 17 The diagram 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. Please refer to... Figure 17 The step S1603 of identifying user equipment for communication methods suitable for non-terrestrial networks (NTNs) includes the following steps:

[0212] Step S1701: Based on a specific preamble of a specific user equipment, and according to the candidate values ​​of residual frequency error and residual time error, perform symbol-level correlation analysis on the received signal to obtain a plurality of symbol-level correlation results. For example, as in the above embodiment, the above two-dimensional correlation operation is performed on each preamble and the received signal. In order to calculate the candidate values ​​of residual time error and residual frequency error, each preamble also needs to be individually delayed, such as... The aforementioned 'n' is the residual time error factor (RTE index), and the aforementioned delayed preamble... It also needs to be multiplied by the frequency-shifted complex exponential sequence e of the candidate value of the carrier residual frequency error (i.e., MΔf). j2πMΔfk , where M is the factor of residual frequency error.

[0213] 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 same intuitive method as the mathematical derivation, multiple similarity measures X corresponding to each user device can be calculated. NC,u,L .

[0214] While the above method corresponds to the mathematical derivation results and is a relatively intuitive implementation method, its only drawback is that the amount of computation is too large.

[0215] Figure 18 The diagram 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. Please refer to... Figure 18 The step S1603 of identifying user equipment for communication methods suitable for non-terrestrial networks (NTNs) includes the following steps:

[0216] Step S1801: Perform multiple time delay operations on the received signal r[k] to obtain multiple delayed received signals. The above n is the residual time error factor (RTE index).

[0217] Step S1802: For the received signal and the aforementioned plurality of delayed received signals, perform a frequency shift 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.

[0218] 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.

[0219] Step S1804: According to a frequency hopping mode assigned to a specific user equipment, the above-mentioned frequency upsampling spectrum is reverse-shifted to obtain a plurality of spectral bins corresponding to that specific user equipment. After the reverse spectrum shift, the spectral bins occupied by the spectrum with higher power than the noise power are the spectral blocks caused by the residual frequency error.

[0220] 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.

[0221] 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.

[0222] 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, a two-dimensional similarity measurement is performed on a plurality of candidate residual frequency errors and a plurality of candidate residual time errors for each user equipment. This allows the communication base station to correctly identify active user equipment, thereby increasing the success rate of random access requests from user equipment. Furthermore, the two-dimensional similarity measurement in the preferred embodiments of the present invention can also estimate residual frequency error values ​​and residual time error values. The communication base station can also transmit these estimated residual frequency error values ​​and residual time error values ​​to each corresponding active user equipment. This allows user equipment to reduce multi-user interference and improve communication quality suitable for non-terrestrial networks (NTNs) through self-adjustment of frequency and time.

[0223] 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 and claims of the present invention are within the scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A communication system, characterized in that, include: A communication base station, including: A detection and estimation unit is configured to receive a received signal, 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. as well as A dedicated channel transmission unit, communicating with the detection and estimation unit, is configured to transmit a response to the user equipment deemed to be active.

2. The communication system according to claim 1, characterized in that, When the maximum value exists among multiple similarity measures corresponding to a specific user device that is considered to be active, the detection and estimation unit performs peak search on the similarity measures in the residual frequency error candidate value and the residual time error candidate value to obtain a residual frequency error estimate and a residual time error estimate corresponding to the specific user device. as well as The dedicated channel transmission unit transmits the residual frequency error estimate and the residual time error estimate to the corresponding specific user equipment that is considered to be active through a dedicated channel, so as to adjust the frequency and time.

3. The communication system according to claim 1, characterized in that, The communication base station is used to transmit a communication beam to the Earth's surface, wherein the communication beam covers a specific service area, and further includes: One compensation unit, Before the communication base station broadcasts a main synchronization signal, the compensation unit acquires a frequency domain compensation parameter and a time domain compensation parameter that are pre-calculated and pre-stored by the system parameters. Following the broadcast of the main synchronization signal, the communication 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 from a first preset frequency band in a specification by adjusting the frequency domain compensation parameters. The post-compensation time is obtained by adjusting the time-domain compensation parameters from a first preset time in the specification. This is to compensate for frequency offset and time delay.

4. The communication system according to claim 3, characterized in that, The primary synchronization signal, as defined in the specification, is broadcast on a second preset frequency band and for a second preset time period. The communication base station broadcasts the main synchronization signal in a pre-compensated frequency band and at a pre-compensated time. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using the frequency domain compensation parameters. The pre-compensation time is adjusted from the second preset time to the pre-compensation time using the time-domain compensation parameter.

5. The communication system according to claim 1, characterized in that, The detection and estimation unit includes: Multiple single random access channel similarity measurement units, wherein each single random access channel similarity measurement unit includes: The system comprises multiple symbol-level correlator groups, each including a first input, a second input, and multiple outputs. The first input of each symbol-level correlator group receives the received signal. The second input of the J-th symbol-level correlator group receives the preamble signal of the corresponding user equipment and delays it by (J-1) time units. The multiple outputs of the J-th symbol-level correlator group output the similarity measurement of the corresponding user equipment under various residual frequency error candidate values ​​with a delay of J-1 time units. Where J is a natural number representing the index of the symbol level correlator group, 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.

6. The communication system according to claim 5, characterized in that, Each symbol level correlator group includes: Multiple correlation assessment units, wherein each correlation assessment unit includes: A first multiplication circuit includes a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the first multiplication circuit of each correlation evaluation unit receives a frequency offset signal with a candidate value of residual frequency error, and the second input terminal of the first multiplication circuit of the I single random access channel calculation unit of the Jth symbol level correlator group receives a preamble signal corresponding to the user equipment and is delayed by (J-1) time units. A conjugate circuit includes 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, 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 conjugate circuit. A first shift register group includes multiple shift registers, wherein the input terminal of the first shift register in the first shift register group is coupled to the output terminal of the second multiplication circuit; A first summator includes a plurality of input terminals and an output terminal, wherein each input terminal of the first summator is coupled to the output terminal of each shift register in the first shift register group, and is configured to calculate the sum output by each shift register in the first shift register group; An absolute value square calculator includes an input terminal and an output terminal, wherein the input terminal of the absolute value square calculator is coupled to the output terminal of a first summator calculator and is configured to calculate the square of the absolute value output from the first summator calculator. A second shift register group, comprising 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 includes a plurality of input terminals and an output terminal, wherein each input terminal of the second summator is coupled to the output terminal of each shift register in the second shift register group, and is configured to calculate the sum of the outputs of each shift register in the second shift register group, wherein the second summator of each correlation evaluation unit outputs a plurality of similarity measures corresponding to the residual frequency error candidate value and the delay (J-1) residual time error candidate values ​​of the I active user equipment in the J-th symbol level correlator group of the I single random access channel calculation unit.

7. The communication system according to claim 2, characterized in that, The detection and estimation unit includes: A plurality of delay units, wherein each delay unit includes an input terminal and an output terminal, wherein the input terminal of the first delay unit receives the received signal, and the output terminal of the Pth delay unit is coupled to the input terminal of the (P+1)th delay unit; and A plurality of Full Random Access Channel Correlator (FARC) groups are provided, wherein each FARC group includes an input and a plurality of outputs, wherein the input of the Qth FARC group is coupled to the output of the (Q-1)th delay unit, and the input of the first FARC group receives the received signal. Specifically, the Qth fully random access channel correlator group outputs multiple similarity measurements corresponding to the specific user equipment based on the frequency hopping mode corresponding to the specific user equipment and the different residual frequency error candidate values ​​corresponding to the specific user equipment. Where P and Q are natural numbers, with P being greater than 0 and less than the number of delay units, and Q being greater than 1 and less than the number of correlator groups in the full random access channel.

8. The communication system according to claim 7, characterized in that, Each full random access channel correlator group includes: A frequency shifter includes an input terminal and an output terminal, wherein the input terminal of the frequency shifter of the Qth full random access channel correlator group is coupled to the output terminal of the (Q-1)th delay unit, and is used to shift the received signal to the base frequency with a delay of (Q-1) time units. A low-pass filter includes an input terminal and an output terminal, wherein the input terminal of the low-pass filter is coupled to the output terminal of the frequency shifter; A downsampling unit includes an input terminal and an output terminal, wherein the input terminal of the downsampling unit is coupled to the output terminal of the low-pass filter, and is configured to downsample the signal from the low-pass filter to obtain N / M per symbol. D Data stream of the sample size; A serial-to-parallel converter includes an input terminal and (N / M) D ) output terminals, wherein the input terminal of the serial-to-parallel unit is coupled to the output terminal of the downsampling unit, configured to convert (N / M) D ) data streams are arranged into one (N / M) D ) outputs; A frequency domain upsampling unit, including (N*M) U / M D ) input terminals and (N*M U / M D ) output terminals, wherein the first (N / M) of the frequency domain upsampling unit D The (N / M) input terminals are respectively coupled to the serial-to-parallel conversion unit. D All output terminals of the frequency upsampling unit and the remaining input terminals of the frequency upsampling unit are set to 0, and the output terminal of the frequency upsampling unit is configured to output (N*M) U / M D The result of the point Fourier transform; A frequency hopping de-sampling unit includes a plurality of input terminals and a plurality of output terminals. The plurality of input terminals of the frequency hopping de-sampling unit are respectively coupled to a plurality of output terminals of the frequency upsampling unit. The frequency hopping de-sampling unit reverses the frequency hopping pattern allocated to the specific user equipment and outputs the corresponding frequency block to the plurality of output terminals of the frequency hopping de-sampling unit. A squared and cumulative similarity measurement calculation unit includes a plurality of input terminals and a plurality of output terminals. The squared and cumulative similarity measurement calculation unit calculates the similarity measurement corresponding to various residual frequency error candidate values ​​for a specific user equipment based on the spectral blocks output by the plurality of output terminals of the frequency hopping de-unit, and outputs the result to the plurality of output terminals of the squared and cumulative similarity measurement calculation unit. Among them, N and M D M U Let N be a natural number, representing the number of samples within the symbol duration, and M be a natural number. D M represents the time-domain downsampling factor. U This represents the frequency domain upsampling factor.

9. A communication system, characterized in that, include: A communication base station for transmitting a communication beam to the Earth's surface, wherein the communication beam covers a specific service area; comprising: One compensation unit, Before the communication base station broadcasts a main synchronization signal, the compensation unit acquires a frequency domain compensation parameter and a time domain compensation parameter that are pre-calculated and pre-stored by the system parameters. Following the broadcast of the main synchronization signal, the base station receives a received signal within a post-compensation frequency band and 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. The post-compensation time is obtained by adjusting the time-domain compensation parameters from a first preset time in the specification. This is to compensate for frequency offset and time delay.

10. The communication system according to claim 9, characterized in that, The primary synchronization signal, as defined in the specification, is broadcast on a second preset frequency band and for a second preset time period. The communication base station broadcasts the main synchronization signal in a pre-compensated frequency band and at a pre-compensated time. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using the frequency domain compensation parameters. The pre-compensation time is adjusted from the second preset time to the pre-compensation time using the time-domain compensation parameter.

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

12. The communication system according to claim 11, characterized in that, When the maximum value exists among multiple similarity measures corresponding to a specific user device that is considered to be in an active state, the detection and estimation unit performs peak search on the candidate values ​​of the residual frequency error and the residual time error for the similarity measures to obtain a residual frequency error estimate and a residual time error estimate corresponding to the specific user device. as well as The dedicated channel transmission unit transmits the residual frequency error estimate and the residual time error estimate to the corresponding specific user equipment that is considered to be active through a dedicated channel, so as to adjust the frequency and time.

13. The communication system according to claim 11, characterized in that, The detection and estimation unit includes: Multiple single random access channel similarity measurement units, wherein each single random access channel similarity measurement unit includes: The system comprises multiple symbol-level correlator groups, each including a first input, a second input, and multiple outputs. The first input of each symbol-level correlator group receives the received signal. The second input of the J-th symbol-level correlator group receives the preamble signal of the corresponding user equipment and delays it by (J-1) time units. The multiple outputs of the J-th symbol-level correlator group output the similarity measurement of the corresponding user equipment under various residual frequency error 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 group, 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 according to claim 13, characterized in that, Each symbol level correlator group includes: Multiple correlation assessment units, wherein each correlation assessment unit includes: A first multiplication circuit includes a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the first multiplication circuit of each correlation evaluation unit receives a frequency offset signal with a candidate value of residual frequency error, and the second input terminal of the first multiplication circuit of the I single random access channel calculation unit of the Jth symbol level correlator group receives a preamble signal corresponding to the user equipment and is delayed by (J-1) time units. A conjugate circuit includes 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, 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 conjugate circuit. A first shift register group includes multiple shift registers, wherein the input terminal of the first shift register in the first shift register group is coupled to the output terminal of the second multiplication circuit; A first summator includes a plurality of input terminals and an output terminal, wherein each input terminal of the first summator is coupled to the output terminal of each shift register in the first shift register group, and is configured to calculate the sum output by each shift register in the first shift register group; An absolute value square calculator includes an input terminal and an output terminal, wherein the input terminal of the absolute value square calculator is coupled to the output terminal of a first summator calculator and is configured to calculate the square of the absolute value output from the first summator calculator. A second shift register group, comprising 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 includes a plurality of input terminals and an output terminal, wherein each input terminal of the second summator is coupled to the output terminal of each shift register in the second shift register group, and is configured to calculate the sum of the outputs of each shift register in the second shift register group, wherein the second summator of each correlation evaluation unit outputs a plurality of similarity measures corresponding to the I-th residual frequency error candidate value and the (J-1)-th residual time error candidate value of the 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 according to claim 12, characterized in that, The detection and estimation unit includes: A plurality of delay units, wherein each delay unit includes an input terminal and an output terminal, wherein the input terminal of the first delay unit receives the received signal, and the output terminal of the Pth delay unit is coupled to the input terminal of the (P+1)th delay unit; and Multiple omni-RACH correlator groups are provided, each omni-RACH correlator group including an input and multiple outputs. The input of the Qth omni-RACH correlator group is coupled to the output of the (Q-1)th delay unit, while the input of the first omni-RACH correlator group receives the received signal. Specifically, the Qth fully random access channel correlator group outputs multiple similarity measurements corresponding to the specific user equipment based on the frequency hopping mode corresponding to the specific user equipment and the different residual frequency error candidate values ​​corresponding to the specific user equipment. Where P and Q are natural numbers, with P being greater than 0 and less than the number of delay units, and Q being greater than 1 and less than the number of correlator groups in the full random access channel.

16. The communication system according to claim 15, characterized in that, Each full random access channel correlator group includes: A frequency shifter includes an input terminal and an output terminal, wherein the input terminal of the frequency shifter of the Qth full random access channel correlator group is coupled to the output terminal of the (Q-1)th delay unit, and is used to shift the received signal to the base frequency with a delay of (Q-1) time units. A low-pass filter includes an input terminal and an output terminal, wherein the input terminal of the low-pass filter is coupled to the output terminal of the frequency shifter; A downsampling unit includes an input terminal and an output terminal, wherein the input terminal of the downsampling unit is coupled to the output terminal of the low-pass filter, and is configured to downsample the signal from the low-pass filter to obtain N / M per symbol. D Data stream of the sample size; A serial-to-parallel converter includes an input terminal and (N / M) D ) output terminals, wherein the input terminal of the serial-to-parallel unit is coupled to the output terminal of the downsampling unit, configured to convert (N / M) D ) data streams are arranged into one (N / M) D ) outputs; A frequency domain upsampling unit, including (N*M) U / M D ) input terminals and (N*M U / M D ) output terminals, wherein the first (N / M) of the frequency domain upsampling unit D The (N / M) input terminals are respectively coupled to the serial-to-parallel conversion unit. D All output terminals of the frequency upsampling unit and the remaining input terminals of the frequency upsampling unit are set to 0, and the output terminal of the frequency upsampling unit is configured to output (N*M) U / M D The result of the point Fourier transform; A frequency hopping de-sampling unit includes a plurality of input terminals and a plurality of output terminals. The plurality of input terminals of the frequency hopping de-sampling unit are respectively coupled to a plurality of output terminals of the frequency upsampling unit. The frequency hopping de-sampling unit reverses the frequency hopping pattern assigned to the specific user equipment and outputs the corresponding spectral bins for the specific user equipment to the plurality of output terminals of the frequency hopping de-sampling unit. A squared and cumulative similarity measurement unit includes a plurality of input terminals and a plurality of output terminals. The squared and cumulative similarity measurement 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 plurality of output terminals of the frequency hopping de-unit, and outputs the result to the plurality of output terminals of the squared and cumulative similarity measurement unit. Among them, N and M D M U Let N be a natural number, representing the number of samples within the symbol duration, and M be a natural number. D M represents the time-domain downsampling factor. U This represents the frequency domain upsampling factor.

17. A communication method, characterized in that, include: 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 similarity measures for a majority of residual time error candidate values ​​for each user device; Based on whether the number of similarity measurements corresponding to a user device exceeds a threshold value, it is determined whether the user device is in an active state. as well as Send a response to the user device that is considered to be active.

18. The communication method according to claim 17, characterized in that, Before receiving the received signal, the method further includes: Before a communication base station broadcasts a major synchronization signal, a frequency domain compensation parameter and a time domain compensation parameter are acquired, which are pre-calculated and pre-stored by system parameters. The received signal is received after the main synchronization signal is broadcast, within a post-compensation frequency band and after 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. The post-compensation time is obtained by adjusting the time-domain compensation parameters from a first preset time in the specification. This is to compensate for frequency offset and time delay.

19. The communication method according to claim 18, characterized in that, The main synchronization signal, as defined in the specification, is broadcast on a second preset frequency band and for a second preset time period, and further includes: The main synchronization signal is broadcast in a pre-compensated frequency band and at a pre-compensated time. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using the frequency domain compensation parameters. The pre-compensation time is adjusted from the second preset time to the pre-compensation time using the time-domain compensation parameter.

20. The communication method according to claim 17, characterized in that, Perform two-dimensional correlation function calculations on the aforementioned plurality of user devices, and obtain the aforementioned plurality of candidate values ​​for residual frequency errors and the aforementioned plurality of candidate values ​​for residual time errors for each user device, including: For the received signal, perform a plurality of time delay operations to obtain a plurality of delayed received signals; For the received signal and the aforementioned plurality of delayed received signals, a frequency shift and a time-domain downsampling are performed to obtain a plurality of downsampled symbols; For the above-mentioned downsampled symbols, perform a time-domain to frequency-domain upsampling transformation to obtain the frequency-domain upsampled spectrum; Based on a frequency hopping mode assigned to a specific user equipment, the aforementioned frequency upsampled spectrum is reverse-shifted to obtain a plurality of spectral bins corresponding to the specific user equipment; and Based on the aforementioned multiple spectral intervals corresponding to a specific user device, the similarity measurement corresponding to the specific user device is calculated under different residual frequency error candidate values.

21. The communication method according to claim 17, characterized in that, Perform two-dimensional correlation function calculations on the aforementioned plurality of user devices, and obtain the aforementioned plurality of candidate values ​​for residual frequency errors and the aforementioned plurality of candidate values ​​for residual time errors for each user device, including: Based on a specific preamble of a specific user equipment, and according to residual frequency error and residual time error, a symbol-level correlation analysis is performed on the received signal to obtain multiple symbol-level correlation results; and The similarity measurement of the specific user device is obtained by performing a squared summation similarity measurement on the above-mentioned majority symbol-level correlation results.

22. The communication method according to claim 21, characterized in that, Based on a specific preamble of the specific user equipment, and according to the candidate values ​​of the residual frequency error and the candidate values ​​of the 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: Perform PxQ symbol-level correlation calculations, where the [I,J]th symbol-level correlation calculation includes: The specific preamble of the I-th time delay of the specific user equipment is multiplied by the frequency shift complex exponential sequence of the J-th residual frequency error to obtain the [I,J]-th frequency shift preamble operation result in each first preset time. The result of the [I,J]th frequency-shift preamble operation is multiplied by the received signal to obtain the product of the [I,J]th received signal and the frequency-shift preamble in each first preset time interval; and Over a predetermined number of first predetermined time intervals, the predetermined number of received signals multiplied by the frequency-shifted preamble are accumulated to obtain the correlation result at the [I,J]th symbol level. Where 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 according to claim 21, characterized in that, The similarity measurement for the specific user device is obtained by performing a squared summation similarity measurement on the above-mentioned majority symbol-level correlation results, including: In each second preset time period, the absolute value of the correlation result at the [I,J]th symbol level is squared to obtain a squared absolute symbol level correlation result; and After a second preset number of second preset times, the squared absolute sign-level correlation results of the second preset number are accumulated to obtain the [I,J]th similarity measure.

24. A communication method, characterized in that, include: Before broadcasting a major synchronization signal, a frequency domain compensation parameter and a time domain compensation parameter are obtained, which are pre-calculated and pre-stored by the system parameters. Following the broadcast of the main synchronization signal, 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 parameters from a first preset frequency band in a specification. The post-compensation time is obtained by adjusting the time-domain compensation parameters from a first preset time in the specification. This is to compensate for frequency offset and time delay.

25. The communication method according to claim 24, characterized in that, The primary synchronization signal, as defined in the specification, is broadcast on a second preset frequency band and for a second preset time period, wherein the communication method further includes: The main synchronization signal is broadcast in a pre-compensated frequency band and at a pre-compensated time. The pre-compensation frequency band is adjusted from the second preset frequency band to the pre-compensation frequency band using the frequency domain compensation parameters. The pre-compensation time is adjusted from the second preset time to the pre-compensation time using the time-domain compensation parameter.

26. The communication method according to claim 24, characterized in that, Also includes: 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 similarity measures for a majority of residual time error candidate values ​​for each user device; Based on whether the number of similarity measurements corresponding to a user device exceeds a threshold value, it is determined whether the user device is in an active state. as well as Send a response to the user device that is considered to be active.

27. The communication method according to claim 26, characterized in that, Perform two-dimensional correlation function calculations on the aforementioned plurality of user devices, and obtain the aforementioned plurality of candidate values ​​for residual frequency errors and the aforementioned plurality of candidate values ​​for residual time errors for each user device, including: For the received signal, perform a plurality of time delay operations to obtain a plurality of delayed received signals; For the received signal and the aforementioned plurality of delayed received signals, a frequency shift and a time-domain downsampling are performed to obtain a plurality of downsampled symbols; For the above-mentioned downsampled symbols, a time-domain to frequency-domain upsampling conversion is performed to obtain the frequency upsampled spectrum; Based on a frequency hopping mode assigned to a specific user equipment and residual frequency error, the aforementioned frequency upsampling spectrum is reverse-shifted to obtain a plurality of frequency ranges corresponding to the specific user equipment; and Based on the aforementioned multiple spectral intervals corresponding to a specific user device, the similarity measurement corresponding to the specific user device is calculated under different residual frequency error candidate values.

28. The communication method according to claim 26, characterized in that, Perform two-dimensional correlation function calculations on the aforementioned plurality of user devices, and obtain the aforementioned plurality of candidate values ​​for residual frequency errors and the aforementioned plurality of candidate values ​​for residual time errors for each user device, including: Based on a specific preamble of a specific user equipment, and according to candidate values ​​of residual frequency error and residual time error, a symbol-level correlation analysis is performed on the received signal to obtain multiple symbol-level correlation results; and The similarity measurement of the specific user device is obtained by performing a squared summation similarity measurement on the above-mentioned majority symbol-level correlation results.

29. The communication method according to claim 28, characterized in that, Based on a specific preamble of the specific user equipment, and according to the candidate values ​​of residual frequency error and residual time error, the received signal is subjected to the symbol-level correlation analysis to obtain the majority of symbol-level correlation results, including: Perform PxQ symbol-level correlation calculations, where the [I,J]th symbol-level correlation calculation includes: Multiply the specific preamble of the I-th residual time error candidate value of the specific user equipment with the frequency shift complex exponential sequence of the J-th residual frequency error candidate value to obtain the [I,J]-th frequency shift preamble operation result; The result of the [I,J]th frequency shift preamble operation is multiplied by the received signal to obtain the product result of the [I,J]th received signal and the frequency shift preamble in each first preset time interval; and Over a predetermined number of first predetermined time intervals, the predetermined number of received signals multiplied by the frequency-shifted preamble are accumulated to obtain the correlation result at the [I,J]th symbol level. Where 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 according to claim 28, characterized in that, The similarity measurement for the specific user device is obtained by performing a squared summation similarity measurement on the above-mentioned majority symbol-level correlation results, including: In each second preset time period, the absolute value of the correlation result at the [I,J]th symbol level is squared to obtain a squared absolute symbol level correlation result; and After a second preset number of second preset times, the squared absolute sign-level correlation results of the second preset number are accumulated to obtain the [I,J]th similarity measure.

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