Terahertz frequency band wireless communication system

Abstract

The invention provides a terahertz frequency band wireless communication system, and relates to the field of communication, the terahertz frequency band wireless communication system comprises a channel configuration module, a transmitting module and a receiving module, the channel configuration module configures modulation information of the transmitting module and the receiving module; based on the modulation information, the transmitting module distributes a plurality of independent original data streams obtained from a plurality of different users to respective corresponding terahertz sub-channels for modulation to obtain a plurality of modulated sub-channel signals, and processes the plurality of modulated sub-channel signals to obtain terahertz DSCM signals; the terahertz DSCM signal is transmitted to a free space for wireless transmission; the receiving module processes a terahertz DSCM signal received from a free space based on the modulation information to obtain a plurality of modulation sub-channel signals, and distributes the plurality of modulation sub-channel signals to respective corresponding terahertz sub-channels for recovery to obtain respective corresponding original data streams; therefore, efficient and flexible multi-terahertz sub-channel wireless transmission is realized.

Description

Technical Field

[0001] This disclosure relates to the field of communication technology, specifically to a terahertz band wireless communication system. Background Technology

[0002] With the rapid development of communication technology, modern communication systems have evolved from first-generation analog communication (1G) to fifth-generation digital communication (5G), and are now accelerating towards sixth-generation communication technology (6G). Against the backdrop of this rapid development, terahertz (THz, referring to terahertz waves in the electromagnetic spectrum of 0.1~10THz) communication technology has become a key driver for the realization of future high-speed wireless communication systems due to its superior performance, including high data transmission rates, ultra-wide bandwidth, abundant frequency band resources, and stronger signal security. As the complexity of multi-user application scenarios increases and data traffic continues to grow, traditional communication structures face greater limitations in expanding system capacity and spectral efficiency, thus hindering the realization of high-speed, high-capacity communication systems. Summary of the Invention

[0003] The main purpose of this disclosure is to provide a terahertz band wireless communication system to achieve efficient and flexible multi-terahertz sub-channel wireless transmission, thereby meeting the growing demand of modern communication systems for high data rates, large bandwidth capacity, and support for multi-user scenarios.

[0004] To achieve the above objectives, a first aspect of this disclosure provides a terahertz band wireless communication system, comprising: a channel configuration module, a transmitting module, and a receiving module, wherein... The channel configuration module is used to configure the modulation information of the transmitting module and the receiving module. The modulation information includes: the number and frequency spacing of multiple terahertz sub-channels that divide the terahertz communication frequency band, the carrier frequency, bandwidth and modulation method of each terahertz sub-channel, and the user-sub-channel correspondence of the terahertz sub-channels allocated to different users based on their communication needs. The transmitting module is configured to: based on modulation information, allocate multiple independent raw data streams obtained from multiple different users to their respective corresponding terahertz sub-channels for modulation to obtain multiple modulation sub-channel signals, process the multiple modulation sub-channel signals to obtain terahertz DSCM signals, and transmit the terahertz DSCM signals into free space for wireless transmission. The receiving module is configured to: process the terahertz DSCM signal received from free space based on the modulation information to obtain multiple modulation sub-channel signals, and allocate the multiple modulation sub-channel signals to their respective corresponding terahertz sub-channels for recovery to obtain their respective original data streams.

[0005] In some embodiments of this disclosure, the user-subchannel correspondence for terahertz subchannels allocated to different users based on their different communication needs includes: Based on the communication demand rates of different users, the terahertz sub-channels allocated to users with higher communication demand rates have better frequency response, while those allocated to users with lower communication demand rates have worse frequency response.

[0006] In some embodiments of this disclosure, configuring a corresponding modulation scheme for each terahertz sub-channel includes: If the frequency response characteristics of the terahertz subchannel meet the set criteria, the modulation scheme of the terahertz subchannel will be configured as 16QAM modulation; wherein, the 16QAM modulation scheme includes 16QAM modulation scheme based on single carrier and 16QAM modulation scheme based on orthogonal frequency division multiplexing. If the frequency response characteristics of the terahertz subchannel do not meet the set criteria, the modulation method of the terahertz subchannel will be configured as QPSK modulation. Among them, QPSK modulation includes single-carrier-based QPSK modulation and orthogonal frequency division multiplexing-based QPSK modulation.

[0007] In some embodiments of this disclosure, the total number of terahertz sub-channels is N0. The N0 terahertz sub-channels are ordered in ascending order of frequency. The N1 terahertz sub-channels ordered at the two edge positions are defined as edge sub-channels, and the N2 terahertz sub-channels ordered in the middle position are defined as center sub-channels. N1 + N2 = N0, and N1 is an integer greater than or equal to 2. The edge sub-channels are configured with QPSK modulation, while the center sub-channels are configured with 16QAM modulation.

[0008] In some embodiments of this disclosure, N0=12, N1=4, N2=8, where, The two terahertz sub-channels arranged closer to the edge of the lowest frequency are defined as part of the edge sub-channels, the two terahertz sub-channels arranged closer to the edge of the highest frequency are defined as another part of the edge sub-channels, and the eight terahertz sub-channels arranged closer to the middle of the frequency are defined as the center sub-channels.

[0009] In some embodiments of this disclosure, the total number of terahertz sub-channels is 13, and all terahertz sub-channels are configured with QPSK modulation.

[0010] In some embodiments of this disclosure, the total number of terahertz sub-channels is 11, and all terahertz sub-channels are configured with 16QAM modulation.

[0011] In some embodiments of this disclosure, the transmitting module includes: The transmitter digital signal processor includes: a transmitter terminal channel processing unit corresponding to multiple terahertz sub-channels, each transmitter terminal channel processing unit being used to sequentially map, upsample, and perform root-raised cosine roll-off filtering on its corresponding original data stream using the modulation scheme configured for the terahertz sub-channel, to generate a digital baseband signal, and then performing single-sided modulation and frequency shifting of the digital baseband signal to the corresponding DSCM sub-channel to obtain a modulated sub-channel signal; a frequency domain superposition and multiplexing unit being used to perform frequency domain superposition and multiplexing of the modulated sub-channel signal to generate a digital baseband DSCM signal; and a digital upconversion unit being used to convert the digital baseband DSCM signal to an intermediate frequency to generate a digital intermediate frequency DSCM signal; A digital-to-analog converter is used to convert digital intermediate frequency (DSCM) signals into analog intermediate frequency (DSCM) signals. The first terahertz subharmonic mixer is used to convert the analog intermediate frequency DSCM signal to the terahertz frequency band to generate a terahertz DSCM signal.

[0012] In some embodiments of this disclosure, the receiving module includes: The second terahertz subharmonic mixer is used to convert the terahertz DSCM signal received from free space to an intermediate frequency to generate an analog intermediate frequency DSCM signal. An analog-to-digital converter is used to convert analog intermediate frequency DSCM signals into digital intermediate frequency DSCM signals. The receiver digital signal processor includes: a receiver terminal channel processing unit corresponding to a plurality of terahertz sub-channels, each receiver terminal channel processing unit including a digital down-conversion unit and a low-pass filter; The digital downconversion unit is used to convert the digital intermediate frequency DSCM signal to the baseband, generate a digital baseband DSCM signal, and convert the digital baseband DSCM signal to realize the shift of the modulation sub-channel signal corresponding to the channel processing unit of this receiving terminal from the DSCM sub-channel to the baseband. The low-pass filter is used to filter out other modulation sub-channel signals besides the terahertz sub-channel corresponding to this receiving terminal channel processing unit, so as to obtain the modulation sub-channel signal corresponding to this receiving terminal channel processing unit, thereby enabling the receiving terminal channel processing unit to obtain the original data stream corresponding to the terahertz sub-channel based on its corresponding modulation sub-channel signal.

[0013] In some embodiments of this disclosure, each receiving terminal channel processing unit further includes: The resampling unit is used to perform resampling operations on the modulated subchannel signal corresponding to the channel processing unit of this receiving terminal. The Gram-Schmidt orthogonalization unit is used to perform Gram-Schmidt orthogonalization processing on the signal output by the resampling unit; The retiming processing unit is used to retiming the signal output by the Gram-Schmidt orthogonalization unit. The equalization algorithm unit is configured based on the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit. The equalization algorithm unit is used to perform equalization processing on the signal output by the retiming processing unit. Specifically, when the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit adopts QPSK modulation mode, the equalization algorithm unit adopts constant mode algorithm unit; when the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit adopts 16QAM modulation mode, the equalization algorithm unit adopts cascaded multimode algorithm. The carrier recovery unit includes a frequency offset estimation unit and a phase offset estimation unit. The frequency offset estimation unit is used to estimate the carrier frequency offset of the DSCM sub-channel corresponding to the local receiving terminal channel processing unit and compensate and correct it. The phase offset estimation unit is used to estimate the carrier phase offset of the DSCM sub-channel corresponding to the local receiving terminal channel processing unit and compensate and correct it, so that the carrier recovery unit obtains QPSK symbols or 16QAM symbols. The demapping unit is used to restore the QPSK symbols or 16QAM symbols obtained by the carrier recovery unit to the original data stream corresponding to the channel processing unit of this receiving terminal; The bit error rate calculation unit is used to calculate the bit error rate of a terahertz band wireless communication system.

[0014] The terahertz band wireless communication system provided in this disclosure configures the modulation information of the transmitting and receiving modules through a channel configuration module. Based on the advantages of terahertz communication technology and DSCM technology, it provides a communication scheme for synchronous transmission of multiple signals in the terahertz band using DSCM technology. Leveraging the terahertz band, it achieves a communication system with ultra-high data transmission rate, ultra-wide bandwidth, high security, and high robustness, fully exploiting the potential of frequency band resources and meeting the ever-increasing demands of communication services. Furthermore, by using DSCM technology, the large-bandwidth terahertz band is divided into several smaller-bandwidth terahertz sub-bands, with each sub-band serving one user, thus enabling multi-user communication. This overcomes the disadvantages of traditional communication structures in terms of system capacity and spectral efficiency, achieving efficient and flexible multi-terahertz sub-channel wireless transmission, thereby meeting the growing demands of modern communication systems for high data rates, large bandwidth capacity, and multi-user scenario support. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic block diagram of a terahertz band wireless communication system provided in an embodiment of this disclosure; Figure 2 A schematic diagram illustrating the working principle of a terahertz band wireless communication system based on DSCM provided in an embodiment of this disclosure; Figure 3 A schematic diagram of an apparatus for synchronously transmitting multiple independent THz sub-channels based on DSCM using SC-QPSK or SC-16QAM modulation schemes, provided as an embodiment of this disclosure; Figure 4 A schematic diagram of the bit error rate of each sub-channel at the receiving end when multiple THz sub-channels using SC-QPSK modulation are transmitted synchronously according to an embodiment of this disclosure. Figure 5 The spectrum diagrams of the transmitter and receiver when 19 THz sub-channels using SC-QPSK modulation are transmitted synchronously according to an embodiment of this disclosure; Figure 6 The bit error rate of the system and the spectrum of the receiver when 13 and 14 THz sub-channels using SC-QPSK modulation are transmitted synchronously according to an embodiment of this disclosure; Figure 7 A schematic diagram of the bit error rate of each sub-channel at the receiving end when synchronously transmitting multiple THz sub-channels using SC-16QAM modulation according to an embodiment of this disclosure; Figure 8 The spectrum diagrams of the transmitter and receiver when 19 THz sub-channels using SC-16QAM modulation are transmitted synchronously according to an embodiment of this disclosure; Figure 9 The bit error rate and receiver spectrum of the system when 11 and 12 THz sub-channels using SC-16QAM modulation are transmitted synchronously according to an embodiment of this disclosure; Figure 10 This is a schematic diagram comparing the system performance of 12 and 13 THz sub-channels synchronously transmitted using hybrid modulation of SC-QPSK and SC-16QAM, according to an embodiment of this disclosure.

[0017] It should be noted that the elements in the attached diagram are schematic and not drawn to scale. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present disclosure, the technical solutions of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present disclosure, and not all embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present disclosure.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] In this disclosure, the terms “upper,” “lower,” “left,” “right,” “front,” “rear,” “top,” “bottom,” “inner,” “outer,” and “middle,” etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are primarily for the purpose of better describing this disclosure and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain circumstances to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this disclosure according to the specific circumstances.

[0022] Furthermore, the terms "set up," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection via an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this disclosure according to the specific circumstances.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other. This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] With the rapid development of modern communication technology, modern communication systems have iterated from the first-generation analog communication systems to the fifth-generation digital communication systems, and are now rapidly advancing towards the sixth-generation communication technology. Compared with 5G, 6G has achieved several orders of magnitude improvements in several key performance indicators such as peak data rate, spectral efficiency, latency, and reliability, thus significantly enhancing the user experience. Therefore, 6G technology is becoming a central focus of global scientific and technological research.

[0025] refer to Figure 1 This disclosure provides a terahertz band wireless communication system designed to address the needs of modern communication systems in terms of high data rates, large bandwidth capacity, and support for multi-user scenarios. The system includes a channel configuration module, a transmitting module, and a receiving module. The channel configuration module is used to configure the modulation information of the transmitting and receiving modules. The modulation information includes: the number and frequency spacing of multiple terahertz sub-channels that divide the terahertz communication frequency band, the carrier frequency, bandwidth and modulation method of each terahertz sub-channel, and the user-sub-channel correspondence of terahertz sub-channels allocated to different users based on different user communication needs. That is, the number of THz sub-channels, the frequency spacing, and the carrier frequency, bandwidth and modulation method used by each THz sub-channel can all be flexibly set through software definition.

[0026] The transmitting module is configured to: based on modulation information, allocate multiple independent raw data streams obtained from multiple different users to their respective corresponding terahertz sub-channels for modulation to obtain multiple modulation sub-channel signals, process the multiple modulation sub-channel signals to obtain terahertz DSCM signals, and transmit the terahertz DSCM signals into free space for wireless transmission.

[0027] The receiving module is configured to: process the terahertz DSCM signal received from free space based on the modulation information to obtain multiple modulation sub-channel signals, and allocate the multiple modulation sub-channel signals to their respective corresponding terahertz sub-channels for recovery to obtain their respective original data streams.

[0028] This disclosure uses the terahertz band as the system's communication band. Terahertz (THz) waves, with a frequency range from 0.1 THz to 10 THz, lie in the transition region between the microwave and infrared spectra and are promising candidate waves for addressing the ever-increasing data traffic demands of future 6G wireless networks. Terahertz communication, with its abundant bandwidth and ultra-high spectrum resources, can meet the diverse needs of multiple users. Furthermore, through deep integration with advanced technologies such as multidimensional modulation, the transmission capacity of the communication system can be significantly enhanced, and spectral efficiency improved.

[0029] Due to its ultra-wide bandwidth and abundant spectrum resources, the terahertz band is expected to support data transmission rates of up to terabits per second (Tbps), enabling high-speed connections for a large number of devices and serving as a fundamental enabling technology for future communication networks. A data link with a carrier frequency of 220 GHz can achieve a transmission rate of up to 25 Gbit / s. Furthermore, a single-input single-output (SISO) fiber optic wireless converged link at 237.5 GHz achieved a data rate of 100 Gbit / s over a distance of 20 meters. With its significant advantages such as high data rate, wide bandwidth, strong security, strong anti-interference capability, and abundant spectrum resources, terahertz communication technology is becoming a key supporting technology for future high-speed wireless communication systems.

[0030] Digital Subcarrier Multiplexing (DSCM) technology decomposes a high-speed single-carrier signal into multiple low-speed subcarrier signals, enabling each subcarrier to independently carry a data stream, thus effectively addressing the challenges posed by modern high-speed communication systems. This method enables flexible adaptive modulation and achieves near-zero frequency crosstalk by independently selecting the symbol rate and allocating the modulation order of each subcarrier, thereby greatly simplifying receiver design.

[0031] DSCM technology can effectively mitigate the effects of equalization-enhanced phase noise. Furthermore, due to the non-overlapping nature of DSCM signals in the frequency domain, this technique exhibits superior performance in mitigating frequency domain impairments, particularly linear impairments. Additionally, by dividing the signal into multiple subcarriers, the symbol rate of each subcarrier is reduced, thereby effectively mitigating the interaction between phase noise and dispersion.

[0032] Furthermore, the implementation of DSCM technology significantly enhances system flexibility, thereby effectively reducing capital expenditure and operating costs of optical networks. Based on these advantages, using DSCM technology to achieve synchronous transmission of multiple signals in the terahertz band not only enables ultra-high data rates, ultra-wideband, high security, and robust anti-interference signal transmission, fully tapping the potential of spectrum resources, but also meets the ever-growing and diversified communication service demands.

[0033] With the increasing number of wireless communication users and the growing diversification of service demands, the need for multi-user application scenarios is constantly emerging. To meet the growing demands of modern communication systems for high data rates, large bandwidth capacity, and support for multi-user scenarios, this disclosure presents a multi-independent THz subchannel synchronous transmission scheme based on Digital Subcarrier Multiplexing (DSCM) technology. DSCM technology decomposes a high-speed single-carrier terahertz signal into multiple subcarrier signals. Terahertz communication technology, with its high data transmission rate, ultra-wide bandwidth, abundant frequency band resources, and high security, is a key technology for solving the data traffic requirements of 6G wireless networks and an enabling technology for future high-speed wireless communication systems. Terahertz communication technology has great development potential, and it is expected to support data transmission rates of terabits per second. It can realize a data link with a carrier frequency of 220 GHz and a transmission rate of 25 Gbit / s; and a single-input single-output fiber-optic wireless converged link with a carrier frequency of 237.5 GHz and a transmission rate of 100 Gbit / s. This demonstrates the great potential of terahertz technology in improving the communication rate of modern communication systems. Meanwhile, Digital Subcarrier Multiplexing (DSCM) technology, which decomposes a high-speed single-carrier signal into multiple low-speed subcarrier signals, allows each terahertz subcarrier to transmit a data stream independently, effectively meeting the high-speed communication requirements of modern communication systems. Furthermore, for terahertz channels using DSCM, different modulation schemes at the receiver exhibit different spectral characteristics and bit error rate performance. How to fully leverage the advantages of different modulation schemes is also a problem worthy of further research.

[0034] The system provided in this disclosure configures the modulation information of the transmitting and receiving modules through a channel configuration module. Based on the advantages of terahertz communication technology and DSCM technology, it provides a communication scheme that uses DSCM technology to achieve synchronous transmission of multiple signals in the terahertz band. By leveraging the terahertz band, it achieves a communication system with ultra-high data transmission rate, ultra-wide bandwidth, high security, and high robustness, fully exploring the potential of frequency band resources and meeting the growing demand for communication services. Furthermore, by using DSCM technology, the large-bandwidth terahertz band is divided into several small-bandwidth terahertz sub-bands, with each terahertz sub-band serving one user, thereby realizing communication for multiple users.

[0035] For example, the transmitting module, acting as the transmitter, can map multiple independent raw data streams onto different terahertz sub-channels at a specified carrier frequency using methods such as single-sideband modulation to obtain multiple modulated sub-channel signals. These signals are then multiplexed in the digital domain by superimposing them in the frequency domain to generate a baseband DSCM signal. For instance, in the digital signal processing stage of the transmitting module, single-sideband (SSB) modulation can be used to generate a digital baseband DSCM signal. Subsequently, up-conversion operations in the digital and analog domains are performed to convert the DSCM signal from the baseband to the THz frequency band. Specifically, the baseband DSCM signal then undergoes a two-stage up-conversion process: a digital up-conversion from the baseband to the intermediate frequency (IF), and an analog up-conversion from the IF to the terahertz carrier frequency, to generate a terahertz DSCM signal. The terahertz DSCM signal consists of multiple independent terahertz sub-channels and is then radiated into free space for wireless transmission.

[0036] As the receiving end of the receiving module, the received terahertz DSCM signal undergoes a two-stage down-conversion process: first, an analog down-conversion from the terahertz carrier frequency to the intermediate frequency (IF), and second, a digital down-conversion from the IF to the baseband, thereby recovering the original transmitted baseband DSCM signal. Digital signal processing is then used to demultiplex the baseband DSCM signal in the digital domain, obtaining multiple modulation sub-channel signals. Finally, the same digital processing framework is used to recover the original transmitted data stream from each terahertz sub-channel.

[0037] The system disclosed herein implements software-defined configuration of key parameters such as the number of terahertz sub-channels, their frequency spacing, carrier frequency, bandwidth allocation, and modulation scheme through a channel configuration module. This enables efficient and flexible multi-terahertz sub-channel wireless transmission, adaptable to diverse user application scenarios. For example, each user's communication needs, such as bandwidth, modulation format, and rate, may differ. Traditional communication systems often use the same and fixed communication methods for different users. However, this disclosure allows for software-defined settings of different bandwidths, modulation formats, and rates for different users, fully meeting their diverse communication needs. The communication system designed in this disclosure is highly flexible. It overcomes the disadvantages of traditional communication structures in terms of system capacity and spectral efficiency, achieving efficient and flexible multi-terahertz sub-channel wireless transmission, thereby meeting the growing demands of modern communication systems for high data rates, large bandwidth capacity, and multi-user scenario support.

[0038] The terahertz band wireless communication system of this disclosure will now be described in detail with reference to the accompanying drawings.

[0039] There are several ways to assign terahertz subchannels to different users based on their communication needs. Some of these methods are illustrated below.

[0040] For example, the user-subchannel mapping relationship for terahertz subchannels allocated to different users based on their communication needs can include: based on the communication rate requirements of different users, users with higher communication rate requirements are allocated terahertz subchannels with better frequency response, while users with lower communication rate requirements are allocated terahertz subchannels with worse frequency response. That is, embodiments of this disclosure can also utilize software-defined technology to allocate terahertz subchannels with good frequency response to users with high rate requirements and terahertz subchannels with poor frequency response to users with low rate requirements through a channel configuration module. Allocating terahertz subchannels that meet the communication needs of different users allows the communication system to flexibly and efficiently handle multi-user application scenarios.

[0041] There are several ways to configure the corresponding modulation scheme for each terahertz sub-channel. Some of these methods are illustrated below.

[0042] For example, configuring a corresponding modulation scheme for each terahertz sub-channel may include: if the frequency response characteristics of the terahertz sub-channel meet a set standard, then the modulation scheme of the terahertz sub-channel is configured as 16QAM modulation; wherein, the 16QAM modulation scheme includes single-carrier-based 16QAM modulation and orthogonal frequency division multiplexing (OFDM)-based 16QAM modulation to improve spectral efficiency. If the frequency response characteristics of the terahertz sub-channel do not meet the set standard, then the modulation scheme of the terahertz sub-channel is configured as QPSK modulation to reduce the bit error rate; wherein, the QPSK modulation scheme includes single-carrier-based QPSK modulation (SC-QPSK) and orthogonal frequency division multiplexing (OFDM)-based QPSK modulation. The above method uses a hybrid modulation scheme of QPSK modulation (e.g., SC-QPSK) and 16QAM modulation (e.g., SC-16QAM) to modulate the sub-channel, fully combining the advantages of both modulation methods and effectively mitigating the inherent non-flat frequency response characteristics of the terahertz communication system.

[0043] Specifically, for terahertz subchannels multiplexed by digital subcarriers, some embodiments of this disclosure use single-carrier-based quadrature phase-shift keying (SC-QPSK) and single-carrier-based 16-Ary quadrature amplitude modulation (SC-16QAM) for synchronous transmission. Building upon this, to better adapt to the non-flat frequency response of terahertz communication systems and enhance their operational flexibility, embodiments of this disclosure propose a novel adaptive modulation communication scheme. For terahertz subchannels exhibiting good frequency response characteristics (meeting set criteria), SC-16QAM modulation is used to maximize spectral efficiency; conversely, for terahertz subchannels with degraded frequency response (not meeting set criteria), SC-QPSK modulation is used to reduce the required signal-to-noise ratio.

[0044] It should be noted that Single-Carrier-Based Quadrature-Phase-Shift-Keying (SC-QPSK) is a modulation technique that transmits 2 bits of information within a symbol by modulating the phase of a single carrier in four different states. Single-Carrier-Based 16-Ary Quadrature-Amplitude-Modulation (SC-16QAM) is a higher-order modulation technique that generates 16 different symbol states by simultaneously modulating the amplitude and phase of a single carrier, thereby transmitting 4 bits of information within each symbol.

[0045] For example, the total number of terahertz sub-channels is N0. The N0 terahertz sub-channels are ordered in ascending order of frequency. The N1 terahertz sub-channels at the two edge positions are defined as edge sub-channels, and the N2 terahertz sub-channels at the middle position are defined as center sub-channels. N1 + N2 = N0, and N1 is an integer greater than or equal to 2. The modulation mode of the edge sub-channels is configured as QPSK modulation mode, and the modulation mode of the center sub-channels is configured as 16QAM modulation mode.

[0046] Specifically, this embodiment utilizes a software-defined channel configuration module, employing multiple terahertz sub-channels with hybrid modulation of SC-QPSK and SC-16QAM for wireless synchronous transmission. The terahertz frequency band is used as the system's communication band, significantly improving data transmission rate, bandwidth, security, anti-interference capability, and spectrum resources, fully leveraging the potential of terahertz technology. DSCM technology decomposes the high-speed single-carrier signal into low-speed subcarrier signals, with each subcarrier corresponding to one user, supporting multi-user application scenarios. Furthermore, DSCM technology allows independent selection of subcarrier symbol rate and modulation order, simplifying receiver module design. It also effectively mitigates equalization enhancement phase noise, linear frequency domain impairments, phase noise, and dispersion, improving system flexibility and reducing operating costs.

[0047] To address the non-flat frequency response phenomenon, i.e., edge frequency response degradation, that occurs when using terahertz channels for communication, the above approach proposes a hybrid modulation communication scheme of SC-QPSK and SC-16QAM. The edge sub-channels use QPSK modulation to reduce the bit error rate, while the central sub-channel uses 16QAM to improve spectral efficiency. This fully combines the advantages of both modulation methods, effectively mitigating the inherent non-flat frequency response characteristics of terahertz communication systems.

[0048] For example, N0=12, N1=4, N2=8, where the two terahertz sub-channels arranged near the edge with the lowest frequency are defined as part of the edge sub-channels, the two terahertz sub-channels arranged near the edge with the highest frequency are defined as another part of the edge sub-channels, and the eight terahertz sub-channels arranged near the middle of the frequency range are defined as the center sub-channels. For example, the 12 terahertz sub-channels, arranged in ascending order of frequency, can be designated as sub-channels 1, 2, 3, ..., 11, 12. The edge sub-channels are sub-channels 1, 2, 11, and 12, using the SC-QPSK modulation scheme, while the other sub-channels are the center sub-channels, using the SC-16QAM modulation scheme.

[0049] After rigorous verification, a system configuration with 4 edge sub-channels (e.g., terahertz sub-channels using SC-QPSK modulation) and 8 center sub-channels (e.g., terahertz sub-channels using SC-16QAM modulation) can support normal communication. The allocation of edge and center sub-channels can be flexibly adjusted based on real-time channel frequency response.

[0050] It should be understood that the number and modulation method of terahertz sub-channels are not limited to those shown above; other methods may also be used.

[0051] For example, the total number of terahertz sub-channels is 13, and all terahertz sub-channels are configured with QPSK modulation. For instance, the system provided in this embodiment can support 13 sub-channel schemes with full SC-QPSK modulation, thus allowing for flexible adjustment according to specific application scenarios.

[0052] For example, the total number of terahertz sub-channels is 11, and all terahertz sub-channels are configured with 16QAM modulation. For instance, the system provided in this embodiment can support 13 sub-channel schemes with full SC-16QAM modulation, thus allowing for flexible adjustment according to specific application scenarios.

[0053] For example, refer to Figure 2 The diagram shown illustrates the principle of synchronous transmission of multiple independent THz sub-channels based on DSCM using SC-QPSK or SC-16QAM modulation schemes. Figure 2 (a) is the spectrum of one of the digital baseband signals after passing through RRC; Figure 2 (b) shows the spectrum of the subchannel with carrier frequency fS1 after SSB modulation; Figure 2 (c) shows the spectrum of each sub-channel after SSB modulation; Figure 2 (d) shows the spectrum of the intermediate frequency DSCM signal obtained through digital up-conversion processing; Figure 2 (e) represents the DSCM signal spectrum of the terahertz subchannel CH.1 after digital downconversion; Figure 2 (f) represents the spectrum after filtering out all sub-channels except CH.1 using LPF and retaining the CH.1 sub-channel.

[0054] refer to Figure 2The transmitting module includes: a transmitting digital signal processor, a digital-to-analog converter, and a first terahertz subharmonic mixer. The transmitting digital signal processor includes: a transmitting terminal channel processing unit corresponding to multiple terahertz sub-channels, each transmitting terminal channel processing unit being used to sequentially map, upsample, and perform root-raised cosine roll-off filtering on its corresponding original data stream using the modulation scheme configured for the terahertz sub-channel to generate a digital baseband signal, and then performing single-sided modulation and frequency shifting of the digital baseband signal to the corresponding DSCM sub-channel to obtain a modulated sub-channel signal; a frequency domain superposition and multiplexing unit, used to perform frequency domain superposition and multiplexing of the modulated sub-channel signals to generate a digital baseband DSCM signal; and a digital up-conversion unit, used to convert the digital baseband DSCM signal to an intermediate frequency (IF) to generate a digital IF DSCM signal; a digital-to-analog converter, used to perform digital-to-analog conversion on the digital IF DSCM signal to generate an analog IF DSCM signal; and a first terahertz subharmonic mixer, used to convert the analog IF DSCM signal to the terahertz frequency band to generate a terahertz DSCM signal.

[0055] For example, refer to Figure 2 The processing steps at the transmitting end include the following: Step 1: The transmitter digital signal processor (TX-DSP) generates N independent QPSK or 16QAM signals as N independent raw data streams; Step 2: Assign the above N signals (N independent raw data streams) to each terahertz sub-channel for specialized signal processing and modulation. Specifically, this includes: First, generating N independent pseudo-random binary sequences (PBRS). Then, performing QPSK or 16QAM mapping, upsampling, and root-raised cosine (RRC) roll-off filtering on these N pseudo-random binary sequences to generate N digital baseband signals; Step 3: Using single-sideband (SSB) modulation technology, each digital baseband signal is frequency-shifted to the subcarrier of its corresponding DSCM subchannel to obtain the modulated subchannel signal; Step 4: Multiplex the N modulated sub-channel signals in the digital frequency domain to generate a digital baseband DSCM signal; Step 5: Upconvert the digital baseband DSCM signal from baseband digital to intermediate frequency to generate a digital intermediate frequency DSCM signal; Step 6: Send the digital intermediate frequency (IF) DSCM signal into the digital-to-analog converter, and then upconvert the signal from the IF analog frequency to the terahertz band to generate a terahertz analog DSCM signal. Step 7: Amplify the terahertz analog DSCM signal using a low-noise amplifier (LNA), and then radiate it into free space via a terahertz antenna.

[0056] Specifically, the steps at the transmitting end include: generating N independent QPSK or 16QAM signals using the TX-DSP; generating N independent PBRS signals, then mapping them to QPSK and 16QAM, upsampling them, and applying RRC roll-off filtering to generate a digital baseband signal; using SSB technology to frequency-shift the digital baseband signal to the sub-channel carrier; generating a digital baseband DSCM signal through digital-domain frequency-domain superposition and multiplexing; converting the digital baseband DSCM signal to a terahertz DSCM signal through two-stage upconversion operations; and transmitting the signal into free space through an LNA.

[0057] In some embodiments, reference Figure 2 The transmitter digital signal processing (TX-DSP) first generates multiple independent QPSK or 16QAM signals required for transmission. These are then assigned to individual sub-channels for dedicated signal processing. Assuming there are N sub-channels, N independent pseudo-random binary sequences (PBRS) are first generated; then, each sequence is QPSK or 16QAM mapped, upsampled, and subjected to root-raised cosine (RRC) roll-off filtering to generate N independent QPSK or 16QAM modulated digital baseband signals. Figure 2 (a) shows the spectrum of one of the digital baseband signals. Subsequently, each signal is modulated by single-sideband (SSB) and frequency-shifted to a sub-channel with a different carrier frequency. Figure 2 (b) is the carrier frequency after SSB modulation. f S1 The sub-channel spectrum is shown at the location. Then, the N modulation sub-channels are frequency-domain superimposed and multiplexed in the digital frequency domain to generate a digital baseband DSCM signal. The sub-channels are numbered in ascending order of carrier frequency, denoted as: CH.1, CH.2, …, CH.N. Figure 2 (c) is the obtained digital baseband DSCM signal spectrum, where the carrier frequencies corresponding to sub-channels CH.1 to CH.N are respectively represented as follows: f S1 , f S2 ... f SN It is worth noting that the result of SSB modulation is a complex digital baseband DSCM signal. This is then digitally up-converted to shift the signal from baseband to intermediate frequency.f IF This generates the corresponding digital intermediate frequency (DSCM) signal; the principle spectrum of this signal is as follows: Figure 2 As shown in (d). Importantly, after the first stage of digital up-conversion, the DSCM signal is converted from a complex representation to a real-valued signal. This digital intermediate frequency (IF) DSCM signal is then fed into a digital-to-analog converter (DAC) to be converted to the analog domain. The resulting analog IF DSCM signal is then fed into a terahertz subharmonic mixer for subharmonic mixing, achieving analog up-conversion of the DSCM signal from the IF to the terahertz band. Assume the local oscillator (LO) frequency driving the terahertz subharmonic mixer is... nf LO The carrier frequency fRF of the generated terahertz DSCM signal then satisfies f RF = 2× nf LO + f IF Here, a low-frequency radio frequency source generates a frequency of f LO A sine wave, then it is multiplied by a factor of n The frequency multiplier is then used to drive the subharmonic mixer. The resulting terahertz DSCM signal is amplified using a low-noise amplifier (LNA) to ensure sufficient transmit power and signal-to-noise ratio for reliable wireless transmission. The amplified signal is then radiated into free space through a terahertz horn antenna.

[0058] For example, the receiving module includes: a second terahertz subharmonic mixer, an analog-to-digital converter, and a receiving-end digital signal processor. The second terahertz subharmonic mixer is used to convert the terahertz DSCM signal received from free space to an intermediate frequency (IF) to generate an analog IF DSCM signal; the analog-to-digital converter is used to perform analog-to-digital conversion on the analog IF DSCM signal to generate a digital IF DSCM signal. The receiving-end digital signal processor includes: a receiving-end channel processing unit corresponding one-to-one with multiple terahertz sub-channels, each receiving-end channel processing unit including a digital down-conversion unit and a low-pass filter.

[0059] The digital down-conversion unit is used to convert the digital intermediate frequency (IF) DSCM signal to baseband, generating a digital baseband DSCM signal. It then further converts the digital baseband DSCM signal to shift the modulation sub-channel signal corresponding to this receiver terminal channel processing unit from the DSCM sub-channel to the baseband. A low-pass filter is used to filter out modulation sub-channel signals other than the terahertz sub-channel corresponding to this receiver terminal channel processing unit, obtaining the modulation sub-channel signal corresponding to this receiver terminal channel processing unit. This allows the receiver terminal channel processing unit to obtain the original data stream corresponding to the terahertz sub-channel based on its corresponding modulation sub-channel signal. Specifically, the receiver-side digital signal processor (RX-DSP) has the following functions: ① Performs digital down-conversion of the DSCM signal from IF to baseband. Unlike the first stage of digital up-conversion in the TX-DSP, the digital down-conversion in the RX-DSP requires further processing. ② Performs down-conversion of each sub-channel in the baseband DSCM signal from its carrier frequency fS1, fS2, ..., fSN to the baseband. Therefore, the receiver's digital down-conversion has two functions: ① down-converting the DSCM signal from the intermediate frequency to the baseband, and ② down-converting a specific sub-channel from its carrier frequency to the baseband. Only then is low-pass filtering performed for that specific DSCM sub-channel.

[0060] For example, each receiving terminal channel processing unit may further include: a resampling unit, a Gram-Schmidt orthogonalization unit, a retiming processing unit, an equalization algorithm unit, a carrier recovery unit, a demapping unit, and a bit error rate calculation unit. The resampling unit performs resampling on the modulation sub-channel signal corresponding to this receiving terminal channel processing unit; the Gram-Schmidt orthogonalization unit performs Gram-Schmidt orthogonalization processing on the signal output by the resampling unit; the retiming processing unit performs retiming processing on the signal output by the Gram-Schmidt orthogonalization unit; and the equalization algorithm unit is configured based on the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit, and performs equalization processing on the signal output by the retiming processing unit. When the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit adopts QPSK modulation mode, the equalization algorithm unit adopts a constant mode algorithm unit; when the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit adopts 16QAM modulation mode, the equalization algorithm unit adopts a cascaded multimode algorithm. The carrier recovery unit includes a frequency offset estimation unit and a phase offset estimation unit. The frequency offset estimation unit estimates and compensates for the carrier frequency offset of the DSCM sub-channel corresponding to the current receiver terminal channel processing unit. The phase offset estimation unit estimates and compensates for the carrier phase offset of the DSCM sub-channel corresponding to the current receiver terminal channel processing unit, thereby enabling the carrier recovery unit to obtain QPSK symbols or 16QAM symbols. The demapping unit recovers the QPSK symbols or 16QAM symbols obtained by the carrier recovery unit back to the original data stream corresponding to the current receiver terminal channel processing unit. Specifically, the demapping unit can be a QAM demapping unit or a QPSK demapping unit. The bit error rate calculation unit calculates the bit error rate of the terahertz band wireless communication system to analyze the performance of the terahertz band wireless communication system.

[0061] For example, refer to Figure 2 The processing steps at the receiving end include the following: Step 1: Receive the terahertz DSCM signal and downconvert the terahertz DSCM signal from the terahertz band to the intermediate frequency to generate an analog intermediate frequency DSCM signal; Step 2: Send the analog intermediate frequency DSCM signal to the analog-to-digital converter for digitization; Step 3: The digital intermediate frequency (DSCM) signal is down-converted from the intermediate frequency to the baseband using the receiver digital signal processing (RX-DSP). Step 4: Taking sub-channel 1 as an example, use a low-pass filter (LPF) to filter out all other sub-channels except sub-channel 1; Step 5: Perform a resampling operation on baseband sub-channel 1, followed by Gram-Schmidt Orthogonalization Procedure (GSOP) and retiming processing; Step 6: Select the appropriate equalization algorithm based on the signal type of sub-channel 1. The constant modulus algorithm (CMA) is used for QPSK signals, and the cascaded multi-modulus algorithm (CMMA) is used for 16QAM signals.

[0062] Step 7: Demapping of QPSK or 16QAM signals is achieved through carrier recovery, which facilitates the reconstruction of the original data stream and the calculation of the bit error rate.

[0063] Specifically, the receiving end steps include: converting the terahertz DSCM signal into a digital baseband DSCM signal through two-stage downconversion; filtering out irrelevant sub-channels using LPF; resampling, GSOP, and retiming processing of the target sub-channel; selecting the appropriate equalization algorithm according to the modulation scheme of the target channel; and demapping the signal through carrier recovery.

[0064] In some embodiments, at the receiver, a two-stage down-conversion operation, reversed from the transmitter's, is performed to recover the original signal. Specifically, the terahertz DSCM signal received by the terahertz horn antenna is first routed to the same subharmonic mixer as the transmitter to achieve a return from the terahertz band to the intermediate frequency. f IF The analog down-conversion is performed. The resulting intermediate frequency (IF) DSCM signal is then amplified by an intermediate frequency amplifier and sent to an analog-to-digital converter (ADC) for digitization. Subsequently, the DSCM signal undergoes digital down-conversion from IF to baseband within the receiver's digital signal processor (RX-DSP) module. Notably, the digital down-conversion in the RX-DSP module also performs separate down-conversion from its respective carrier wave for each sub-channel of the baseband DSCM signal. f S1 , f S2 ... f SN Down-conversion to baseband. Taking subchannel CH.1 as an example, the carrier frequency is down-converted through a digital down-conversion process. f S1 + f IF Down-convert to baseband Figure 2 (e) demonstrates the DSCM signal generated by f S1 + f IF The spectrum after downconversion to baseband. Subsequently, a low-pass filter (LPF) is used to filter out all sub-channels except CH.1, such as... Figure 2 As shown in (f). Then, the baseband subchannel CH.1 is resampled, followed by a Gram-Schmidt Orthogonalization Procedure (GSOP) and retiming. Next, an appropriate equalization algorithm is selected based on the type of signal carried by subchannel CH.1; when CH.1 carries a QPSK signal, the Constant Modulus Algorithm (CMA) is used; when CH.1 carries a 16QAM signal, the Cascaded Multi-Modulus Algorithm (CMMA) is used. After equalization, additional signal processing steps are performed, including carrier recovery, to demap the QPSK or 16QAM signal in subchannel CH.1. This process facilitates the reconstruction of the original transmitted data stream and the calculation of the BER. Similarly, the same processing steps are sequentially applied to each of the remaining subchannels. In other words, by utilizing digital signal processing techniques, the DSCM signal can be effectively demultiplexed, and the multiple original data streams it carries can be successfully recovered. It is worth noting that although single-carrier modulation was used for all sub-channels in the theoretical description and subsequent experimental verification in this section, the proposed framework can theoretically be extended to orthogonal frequency division multiplexing (OFDM) modulation.

[0065] Application Product: The experiment was conducted in a 220GHz all-electronic communication system using a Single-Input Single-Output (SISO) wireless link. This invention primarily aims to overcome the limitations of traditional communication systems in terms of system capacity and spectral efficiency. It utilizes the ultra-wide bandwidth and high data rate characteristics of the terahertz band to meet the demands of modern communication systems for high data rates, large bandwidth capacity, and multi-user scenarios. Therefore, this invention can be applied to terahertz wireless communication scenarios.

[0066] Experimental verification was conducted in a 220 GHz all-electronic communication system using a Single-Input Single-Output (SISO) wireless link. Results show that when using single-carrier quadrature phase-shift keying (SC-QPSK) or single-carrier hexadecimal quadrature amplitude modulation (SC-16QAM) to simultaneously transmit multiple terahertz sub-channels, the system can successfully support signal transmission for 13 and 11 sub-channels respectively, while maintaining the bit error rate (BER) at the soft-decision forward error correction (SD-FEC) threshold of 2 × 10⁻⁶. -2 The following is an example. Furthermore, the experiment also verified a hybrid transmission scheme, including four SC-QPSK modulation sub-channels and eight SC-16QAM modulation sub-channels. Experimental results confirmed that the bit error rate of all sub-channels was less than 2 × 10⁻⁶. -2 This demonstrates the robust performance of the hybrid SC-QPSK and SC-16QAM modulation scheme. The experimental setup and conclusions are described in detail below.

[0067] like Figure 3 The diagram shows an experimental setup based on DSCM that synchronously transmits multiple independent THz sub-channels using SC-QPSK or SC-16QAM modulation schemes. In this setup, AWG represents an arbitrary waveform generator, LO represents the local oscillator, LNA represents a low-noise amplifier, OSC represents an oscilloscope, TX-DSP represents the transmitter digital signal processor chip, and RX-DSP represents the receiver digital signal processor chip.

[0068] refer to Figure 3In the experimental setup, each terahertz subchannel has a bandwidth of 1 GHz, and the frequency spacing between adjacent terahertz subchannels is 1.1 GHz. SC-QPSK or SC-16QAM is used as the modulation scheme. Using the TX-DSP described in the experimental principle section, a 10 GHz digital intermediate frequency (IF) DSCM signal is obtained after the first-stage digital up-conversion. This signal is then fed into an arbitrary waveform generator with a sampling rate of 64 GSa / s and a 3dB analog bandwidth of 25 GHz to achieve digital-to-analog conversion. The resulting 10 GHz IF analog DSCM signal is fed into a THz subharmonic mixer to complete the second-stage analog up-conversion from the 10 GHz IF to the 220 GHz carrier frequency. The output of a fixed frequency source with an output power of 13 dBm and a frequency of 17.5 GHz generates a 105 GHz LO signal through a 6-fold frequency multiplier, driving the THz subharmonic mixer. The obtained 220 GHz terahertz DSCM signal was amplified using a 25 dB gain LNA and then transmitted via a 0.5 m SISO wireless link. This wireless link consisted of a pair of horn antennas, each with a 25 dB gain and operating in the 170-260 GHz frequency range. The 220 GHz terahertz DSCM signal received by the horn antennas was fed into a terahertz subharmonic mixer for analog down-conversion from 220 GHz to a 10 GHz intermediate frequency. The mixer and its driving local oscillator were identical in structure to those used at the transmitter. The resulting 10 GHz DSCM signal was amplified using a 35 dB intermediate frequency amplifier and then digitized using an oscilloscope (OSC) with a sampling rate of 100 GSa / s and a 3 dB analog bandwidth of 25 GHz. Finally, digital down-conversion and digital demultiplexing of the 10 GHz DSCM signal to baseband were implemented using the RX-DSP described in the theoretical section. It is worth noting that if a terahertz power amplifier is added in front of the horn antenna at the transmitting end and a terahertz LNA is added after the horn antenna at the receiving end, the wireless transmission distance can be extended to tens of meters.

[0069] The experimental results are described below: In subsequent experiments, when multiple SC-QPSK modulated signals were transmitted synchronously, the BER of a single THz subchannel at the receiving end was analyzed, as follows: Figure 4 The diagram shown illustrates the bit error rate of each sub-channel at the receiver when multiple THz sub-channels are transmitted synchronously using SC-QPSK modulation. Figure 4 (a) represents the BER heatmap. Figure 4 (b) shows the BER 3D diagram. Each terahertz subchannel is allocated a bandwidth of 1 GHz, and the frequency spacing between adjacent terahertz subchannels is 1.1 GHz. Figure 4 (a) heatmap and Figure 4(b) shows the 3D plot depicting the BER distribution of all terahertz subchannels with different numbers of terahertz subchannels. The terahertz subchannels are numbered N from 4 to 20. Figure 4 (a) and Figure 4 (b) It can be seen that when N does not exceed 13, the bit error rate of each sub-channel is lower than the SD-FEC threshold of 2×10⁻⁶. -2 This indicates that the system performance is good. However, when N exceeds 13, only the terahertz sub-channel located in the center maintains a low bit error rate, while the performance of the terahertz sub-channel located at the edge of the signal spectrum deteriorates significantly.

[0070] refer to Figure 5 The image shows the spectrum of the transmitter and receiver when 19 THz sub-channels using SC-QPSK modulation are transmitted synchronously. Figure 5 (a) Transmitter spectrum, Figure 5 (b) Receiver spectrum. Figure 5 (a) and Figure 5 (b) shows the spectral characteristics of the transmitter and receiver when 19 terahertz sub-channels are transmitted simultaneously. Figure 5 As shown in (a), the transmission spectrum exhibits a relatively flat distribution in the 0–20 GHz band. However, as Figure 5 As shown in (b), due to the inherent non-flatness of the terahertz component frequency response and other system-level impairments, the sub-channels located at the edges of the signal spectrum experience significant power attenuation relative to the central sub-channels. Figure 4 As shown, the power drop observed at the frequency band edge provides a direct explanation for the significant decrease in bit error rate performance of external sub-channels when the total number of sub-channels exceeds 13.

[0071] To investigate the maximum number of THz sub-channels that can be transmitted simultaneously under SC-QPSK modulation, the bit error rate and received spectrum characteristics of systems transmitting 13 and 14 sub-channels respectively were compared and analyzed. The results are as follows: Figure 6 The diagram shows the system's bit error rate and receiver spectrum when 13 and 14 THz sub-channels are transmitted simultaneously using SC-QPSK modulation. Figure 6 (a) represents the bit error rate of the system when 13 and 14 terahertz sub-channels are transmitted simultaneously; Figure 6 (b) shows the spectrum of the receiver transmitting on 13 terahertz sub-channels; Figure 6 (c) shows the spectrum of the receiver transmitting on 14 terahertz sub-channels.

[0072] Figure 6 (a) presents the bit error rate performance at the receiver for each THz subchannel under two configurations: N=13 and N=14. For example... Figure 6As shown, sub-channels 3 to 10 exhibit excellent BER performance, approximately 1 × 10⁻⁶. -12 The BER of the other sub-channels was significantly higher, all exceeding 1×10⁻⁶. -4 This is related to Figure 4 and Figure 4 The results were consistent, further confirming that the frequency response of the experimental system was non-flat. Figure 6 (a) shows that when N=13, the bit error rate of all sub-channels is less than 2×10⁻⁶. -2 This indicates that the system performance is good. When N increases to 14, the bit error rate of the 14th sub-channel exceeds the threshold. These results show that the BER remains at 2×10⁻⁶ across all sub-channels. -2 Under the following conditions, the system can achieve a total data rate of 13 × 1 × log24 = 26 Gb / s. Figure 6 (b) and Figure 6 (c) shows the received spectrum characteristics for N=13 and N=14 respectively, where the power attenuation of the edge sub-channels is significant compared to the center sub-channel.

[0073] Subsequently, the bit error rate performance of the receiver's THz subchannel under concurrent transmission was further investigated using the SC-16QAM modulation scheme. The results are as follows: Figure 7 The diagram shown illustrates the bit error rate of each sub-channel at the receiver when using SC-16QAM modulation for synchronous transmission across multiple THz sub-channels. Figure 7 (a) represents the BER heatmap. Figure 7 (b) BER 3D plot. Figure 7 (a) heatmap and Figure 7 (b) The three-dimensional plots all show the bit error rate distribution of all terahertz sub-channels under different numbers of simultaneously transmitted terahertz sub-channels. From Figure 7 As can be seen, when the number of terahertz sub-channels N does not exceed 11, the BER values ​​of all terahertz sub-channels are lower than 2 × 10⁻⁶. -2 However, when N exceeds 11, only the terahertz subchannel located at the center maintains a low bit error rate, while the terahertz subchannel located at the edge of the signal spectrum exhibits a significant performance degradation.

[0074] refer to Figure 8 The spectrum diagrams shown are of the transmitter and receiver when 19 THz sub-channels using SC-16QAM modulation are transmitted synchronously. Figure 8 (a) shows the transmitter's spectrum. Figure 8 (b) represents the receiver spectrum. Figure 8 (a) and Figure 8 (b) The spectral characteristics of the transmitter and receiver when 19 terahertz sub-channels are transmitted simultaneously. Figure 8As shown in (a), under SC-16QAM modulation, the transmit spectrum maintains a relatively flat profile in the 0-20 GHz band, which is consistent with... Figure 5 (a) The observed spectral behavior under SC-QPSK modulation is consistent. Similarly, as Figure 8 As shown in (b), due to the inherent non-flatness of the terahertz component frequency response and other system-level impairments, the power attenuation of sub-channels located at the edge of the signal spectrum is significant compared to that of the center sub-channels. When the number of sub-channels N exceeds 11, the decrease in power of the edge sub-channels directly leads to a significant decrease in the bit error rate performance of the edge sub-channels, such as... Figure 7 As shown.

[0075] To investigate the maximum number of THz sub-channels that can be transmitted simultaneously under SC-16QAM modulation, the bit error rate and received spectral characteristics of systems transmitting 11 and 12 sub-channels respectively were compared and analyzed. Experimental results are as follows: Figure 9 The diagram shows the bit error rate and receiver spectrum of the system when 11 and 12 THz sub-channels are transmitted simultaneously using SC-16QAM modulation. Figure 9 (a) The bit error rate of the system when simultaneously transmitting 11 and 12 THz sub-channels; Figure 9 (b) Spectrum diagram of the receiver transmitting on 11 THz sub-channels; Figure 9 (c) Spectrum diagram of the receiver transmitting on 12 THz sub-channels.

[0076] Figure 9 (a) presents the bit error rate performance of each sub-channel at the receiver under two configurations: N=11 and N=12. For example... Figure 9 As shown, when N = 11, the BER of all 11 sub-channels is less than 2 × 10⁻⁶. -2 It is worth noting that specific central sub-channels (e.g., N=6 and N=9) are in 1×10 -12 Excellent BER values ​​were achieved in the vicinity, while the BER values ​​of the sub-channels at the spectrum edge were even higher, all greater than or equal to 1×10⁻⁶. -4 This observation is consistent with... Figure 7 and Figure 8 The results were consistent, further confirming the non-flat frequency response of the experimental setup. However, when the number of sub-channels increased to N=12, the bit error rate of the 12th sub-channel exceeded 2×10⁻⁶. -2 Experimental results show that SC-16QAM modulation is used in all sub-channels with a BER lower than 2×10⁻⁶. -2 Under these conditions, the system can support a total data rate of 11×1×log216=44Gb / s. Figure 9 (b) and Figure 9(c) describes the spectral characteristics for N=11 and N=12, respectively. Compared with the central sub-channel, the power of the edge sub-channels is significantly reduced. The decrease in edge power directly explains the decrease in bit error rate performance when the number of sub-channels increases to 12, thus limiting the maximum number of sub-channels for concurrent transmission.

[0077] To better adapt to the non-flat frequency response of the system and enhance its operational flexibility, embodiments of this disclosure propose a novel adaptive modulation strategy. For terahertz sub-channels exhibiting good frequency response characteristics, SC-16QAM modulation is employed to maximize spectral efficiency; conversely, for terahertz sub-channels with degraded frequency response, SC-QPSK modulation is employed to reduce the required signal-to-noise ratio. Based on the foregoing, it can be observed that when multiple terahertz sub-channels are transmitted simultaneously using SC-QPSK or SC-16QAM modulation, the central sub-channels always have a superior frequency response compared to the edge sub-channels. Utilizing this observation, SC-QPSK modulated signals are allocated to the edge sub-channels, and SC-16QAM modulation is deployed on as many central sub-channels as possible, aiming to achieve optimal overall transmission efficiency.

[0078] In the case of terahertz subchannel transmission using a hybrid SC-QPSK and SC-16QAM architecture, a performance comparison analysis was conducted on systems simultaneously transmitting 12 and 13 subchannels. The results are as follows: Figure 10 The diagram shows a comparison of system performance when 12 and 13 THz sub-channels are transmitted synchronously using a hybrid modulation of SC-QPSK and SC-16QAM. Figure 10 (a) represents the bit error rate of the system when synchronously transmitting 12 and 13 THz sub-channels in the case of mixed transmission; Figure 10 (b) shows the spectrum of the receiver transmitting on 12 THz sub-channels; Figure 10 (c) shows the spectrum of the receiver transmitting on 13 THz sub-channels; Figure 10 (d) represents the system constellation diagram when 12 THz sub-channels are transmitted synchronously under mixed transmission conditions.

[0079] For a 12-subchannel configuration, terahertz subchannels 1, 2, 11, and 12 are designated for SC-QPSK transmission, while the remaining terahertz subchannels carry SC-16QAM signals. In the case of 13 subchannels, subchannels 1, 2, 11, 12, and 13 are allocated to SC-QPSK, and the remaining terahertz subchannels use SC-16QAM. Figure 10 (a) The BER performance of all sub-channels under the two configurations was compared. The results show that when transmitting 12 terahertz sub-channels, the BER value of all terahertz sub-channels remains at 2 × 10⁻⁶. -2However, when the number of terahertz sub-channels was increased to 13, the bit error rate of the 13th terahertz sub-channel exceeded this threshold. Furthermore, compared to... Figure 10 (b) and Figure 10 (c) The received spectrum shows that the spectral attenuation of the 13th sub-channel is more significant in the 13-sub-channel configuration. Figure 10 (d) shows the constellation diagram recovered by the receiver in the case of 12 terahertz sub-channels, clearly demonstrating the SC-QPSK characteristics of terahertz sub-channels 1, 2, 11, and 12. In contrast, the remaining terahertz sub-channels exhibit significant characteristics of SC-16QAM modulation.

[0080] This concludes the description of the terahertz band wireless communication system. It should be understood that, in addition to the functional modules shown above, the terahertz band wireless communication system may also include other functional modules, all of which fall within the protection scope of the terahertz band wireless communication system provided in this disclosure.

[0081] As can be seen from the above description, this disclosure achieves the following technical effects: The software-defined multi-independent THz sub-channel synchronous transmission scheme proposed in the embodiments of this disclosure is implemented based on DSCM technology. Experimental verification was conducted in a fully electronic communication system in the 220 GHz terahertz band. The results show that when all sub-channels are synchronously transmitted using SC-QPSK or SC-16QAM modulation, the system successfully supports 13 and 11 channel configurations respectively, with the bit error rate remaining below the SD-FEC threshold of 2×10⁻². Furthermore, in a hybrid transmission scenario containing 4 SC-QPSK modulated sub-channels and 8 SC-16QAM modulated sub-channels, the bit error rate (BER) of all channels is below the SD-FEC threshold. By providing flexible channel management and adaptive modulation format selection, the proposed scheme enables the system to adapt to diverse application scenarios while ensuring low bit error rate transmission and efficient multi-channel synchronization. This work not only provides new ideas for the development of 6G communication technology but also provides a basic framework for the deployment of future high-capacity THz communication systems.

[0082] Although embodiments of the present disclosure have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present disclosure, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A terahertz band wireless communication system, characterized in that, include: The channel configuration module, the transmitting module, and the receiving module, among which, The channel configuration module is used to configure the modulation information of the transmitting module and the receiving module; the modulation information includes: the number and frequency interval of multiple terahertz sub-channels that divide the terahertz communication frequency band, the carrier frequency, bandwidth and modulation method of each terahertz sub-channel, and the user-sub-channel correspondence of terahertz sub-channels allocated to different users based on different user communication needs. The transmitting module is configured to: based on the modulation information, allocate multiple independent raw data streams obtained from multiple different users to their respective corresponding terahertz sub-channels for modulation to obtain multiple modulation sub-channel signals, process the multiple modulation sub-channel signals to obtain terahertz DSCM signals, and transmit the terahertz DSCM signals into free space for wireless transmission. The receiving module is configured to: process the terahertz DSCM signal received from free space based on the modulation information to obtain the plurality of modulation sub-channel signals, and allocate the plurality of modulation sub-channel signals to their respective corresponding terahertz sub-channels to recover the respective corresponding original data streams.

2. The system as described in claim 1, characterized in that, The user-subchannel correspondence for terahertz subchannels allocated to different users based on their different communication needs includes: Based on the communication demand rates of different users, the terahertz sub-channels allocated to users with higher communication demand rates have better frequency response, while those allocated to users with lower communication demand rates have worse frequency response.

3. The system as described in claim 1, characterized in that, Configuring the corresponding modulation scheme for each terahertz sub-channel includes: If the frequency response characteristics of the terahertz sub-channel meet the set criteria, the modulation scheme of the terahertz sub-channel is configured as 16QAM modulation; wherein, the 16QAM modulation scheme includes a single-carrier-based 16QAM modulation scheme and an orthogonal frequency division multiplexing-based 16QAM modulation scheme. If the frequency response characteristics of the terahertz subchannel do not meet the set standard, the modulation method of the terahertz subchannel will be configured as QPSK modulation; wherein, the QPSK modulation method includes single-carrier-based QPSK modulation and orthogonal frequency division multiplexing-based QPSK modulation.

4. The system as described in claim 1, characterized in that, The total number of terahertz sub-channels is N0. The N0 terahertz sub-channels are ordered in ascending order of frequency. The N1 terahertz sub-channels ordered at the two edge positions are defined as edge sub-channels, and the N2 terahertz sub-channels ordered in the middle position are defined as center sub-channels. N1 + N2 = N0, and N1 is an integer greater than or equal to 2. The edge sub-channel is configured with QPSK modulation, and the center sub-channel is configured with 16QAM modulation.

5. The system as described in claim 4, characterized in that, Where N0=12, N1=4, N2=8, and so on. Two terahertz sub-channels arranged near the edge with the lowest frequency are defined as part of the edge sub-channels, two terahertz sub-channels arranged near the edge with the highest frequency are defined as another part of the edge sub-channels, and eight terahertz sub-channels arranged near the middle of the frequency are defined as the center sub-channels.

6. The system as described in claim 1, characterized in that, The total number of terahertz sub-channels is 13, and all of the terahertz sub-channels are configured with QPSK modulation.

7. The system as described in claim 1, characterized in that, The total number of terahertz sub-channels is 11, and all of the terahertz sub-channels are configured with 16QAM modulation.

8. The system as described in any one of claims 1 to 7, characterized in that, The transmitting module includes: The transmitting digital signal processor includes: Each of the multiple terahertz sub-channels has a corresponding transmitter terminal channel processing unit. Each transmitter terminal channel processing unit is used to map, upsample, and root-raised cosine roll-off filter the corresponding original data stream sequentially using the modulation method configured for the terahertz sub-channel to generate a digital baseband signal. The digital baseband signal is then unilaterally modulated and frequency-shifted to the corresponding DSCM sub-channel to obtain the modulated sub-channel signal. A frequency domain superposition and multiplexing unit is used to perform frequency domain superposition and multiplexing of the modulated sub-channel signals to generate a digital baseband DSCM signal; and... A digital upconversion unit is used to convert the digital baseband DSCM signal to an intermediate frequency to generate a digital intermediate frequency DSCM signal; A digital-to-analog converter is used to convert the digital intermediate frequency (DSCM) signal into an analog intermediate frequency (DSCM) signal. The first terahertz subharmonic mixer is used to convert the analog intermediate frequency DSCM signal to the terahertz frequency band to generate the terahertz DSCM signal.

9. The system as described in claim 8, characterized in that, The receiving module includes: The second terahertz subharmonic mixer is used to convert the terahertz DSCM signal received from free space to an intermediate frequency to generate the analog intermediate frequency DSCM signal. An analog-to-digital converter is used to convert the analog intermediate frequency DSCM signal into a digital intermediate frequency DSCM signal. The receiver digital signal processor includes: a receiver terminal channel processing unit corresponding to each of the plurality of terahertz sub-channels, and each receiver terminal channel processing unit includes a digital down-conversion unit and a low-pass filter; The digital downconversion unit is used to convert the digital intermediate frequency (DSCM) signal to baseband, generate a digital baseband DSCM signal, and convert the digital baseband DSCM signal to realize the shift of the modulation subchannel signal corresponding to the channel processing unit of this receiving terminal from the DSCM subchannel to the baseband. The low-pass filter is used to filter out other modulation sub-channel signals besides the terahertz sub-channel corresponding to this receiving terminal channel processing unit, so as to obtain the modulation sub-channel signal corresponding to this receiving terminal channel processing unit, thereby enabling the receiving terminal channel processing unit to obtain the original data stream corresponding to the terahertz sub-channel based on its corresponding modulation sub-channel signal.

10. The system as described in claim 9, characterized in that, Each of the receiving terminal channel processing units further includes: The resampling unit is used to perform a resampling operation on the modulated subchannel signal corresponding to the channel processing unit of this receiving terminal. The Gram-Schmidt orthogonalization unit is used to perform Gram-Schmidt orthogonalization processing on the signal output by the resampling unit; A retiming processing unit is used to retiming the signal output by the Gram-Schmidt orthogonalization unit. The equalization algorithm unit is configured based on the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit. The equalization algorithm unit is used to perform equalization processing on the signal output by the retiming processing unit. Specifically, when the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit adopts QPSK modulation mode, the equalization algorithm unit adopts constant mode algorithm unit; when the modulation scheme of the terahertz sub-channel corresponding to this receiving terminal channel processing unit adopts 16QAM modulation mode, the equalization algorithm unit adopts cascaded multimode algorithm. The carrier recovery unit includes a frequency offset estimation unit and a phase offset estimation unit. The frequency offset estimation unit is used to estimate the carrier frequency offset of the DSCM sub-channel corresponding to the local receiving terminal channel processing unit and compensate and correct it. The phase offset estimation unit is used to estimate the carrier phase offset of the DSCM sub-channel corresponding to the local receiving terminal channel processing unit and compensate and correct it, so that the carrier recovery unit obtains QPSK symbols or 16QAM symbols. The demapping unit is used to restore the QPSK symbol or the 16QAM symbol obtained by the carrier recovery unit to the original data stream corresponding to the channel processing unit of this receiving terminal; The bit error rate calculation unit is used to calculate the bit error rate of the terahertz band wireless communication system.

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