A frequency domain differential modulation method and system for high-reliability low-latency mobile communication and a storage medium

Abstract

The application provides a frequency domain differential modulation method, system and storage medium for high-reliability and low-latency mobile communication, the frequency domain differential modulation method comprising: step 1: converting B-bit information bits into J-bit coded bits; step 2: mapping the J-bit coded bits into an M-order phase shift keying symbol block, and using a frequency domain differential modulation technology to express information as a phase difference between two adjacent subcarrier signals in the same OFDM symbol; step 3: performing K-point inverse discrete Fourier transform to convert a frequency domain transmission sequence into a time domain transmission sequence, and adding a cyclic prefix in the time domain transmission sequence; step 4: a receiver receives a serial sequence, performs K-point discrete Fourier transform, detects data by comparing subcarrier signals on the same OFDM symbol, and converts the data into B-bit information bits by using a phase shift keying soft demodulator and a channel decoder. The application has the beneficial effect that high-reliability and low-latency mobile communication can be realized at extremely low signaling cost and wireless resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, and particularly relates to a frequency domain differential modulation method and system for high-reliability and low-latency mobile communication and a storage medium. BACKGROUND

[0002] Ultra-reliable and low-latency communications (URLLC) is a major application scenario for 5th generation (5G) and 6th generation (6G) wireless communication networks, which can realize various mission-critical applications such as factory automation, remote surgery, tactile internet and autonomous driving. In order to support these applications, the 3rd generation partnership project (3GPP) specifies the performance requirements of 1 ms physical layer latency and 99.999% reliability for high-reliability and low-latency applications under 5G networks. With the increasing requirements of emerging businesses on network performance, it is expected that the physical layer latency and reliability requirements of high-reliability and low-latency communications in the upcoming 6G network will reach 0.1 ms and 99.99999%, respectively.

[0003] In order to meet such stringent performance requirements in high-reliability and low-latency communications, 3GPP introduces a new feature of mini-slot for 5G networks. Specifically, the mini-slot adopts a set of 2, 4 or 7 OFDM symbols as the basic unit of data scheduling and resource allocation. In contrast, the minimum scheduling unit for the other two main use cases in 5G networks, namely, enhanced mobile broadband (eMBB) and massive machine-type communications (mMTC), is a traditional slot occupying 12 or 14 OFDM symbols. In the traditional slot format, the data packets arriving within the slot have to wait until the end of the slot before being transmitted. In contrast, the mini-slot format with finer time-domain division can start data transmission at any OFDM symbol without waiting for the slot boundary. Therefore, the mini-slot format is particularly suitable for short data packets of tens to hundreds of bytes in size to achieve fast data transmission and transmission response.

[0004] In order to support different business scenarios and use cases in short packet transmission based on the mini-slot format, 3GPP Release 18 defines a fixed pilot symbol deployment to realize channel estimation and data detection. Figure 1(ad) shows the pilot patterns for 2, 4, and 7 OFDM symbol units specified in 3GPP Release 18. Specifically, in order to perform channel estimation and data detection immediately after receiving the data symbol, the pilot symbols are placed on the equally spaced subcarriers of the first OFDM symbol of the mini-slot. In addition, for high mobility scenarios, additional pilot symbols can be deployed in the middle of mini-slots larger than 4 OFDM symbols to improve channel estimation performance, such as Figure 1 (d) shown.

[0005] Depend on Figure 1 As shown in Figure (a), within two OFDM symbols, up to 25% of the radio resources are allocated to pilot symbols for channel estimation. This is very expensive for short packet transmission and significantly impairs the system's latency performance and spectral efficiency. On the other hand, reducing the proportion of pilot symbols leads to a decrease in channel estimation accuracy, which severely degrades data detection performance, especially in high-mobility scenarios with rapidly fluctuating channels. Summary of the Invention

[0006] In order to avoid the signaling cost problem caused by channel estimation, the present invention proposes a frequency domain differential modulation method for high-reliability and low-latency mobile communications to realize short packet transmission based on mini-slot. The frequency domain differential modulation method can encode the transmitted information as the phase difference between adjacent subcarrier signals under the same OFDM symbol, and detect the data by comparing the phase between the two subcarrier signals, thereby avoiding the channel estimation process and greatly reducing the signaling cost.

[0007] The present invention provides a frequency domain differential modulation method for high-reliability and low-latency mobile communications, comprising the following steps:

[0008] Step 1: The transmitter uses a channel encoder to convert B information bits into J coded bits.

[0009] Step 2: For the differentially modulated OFDM system, first map the J coded bits into an M-order phase shift keying symbol block c = {c1, c2, ..., c N},in is the constellation alphabet of the M-order PSK symbol, and assuming that N is an integer, then the N PSK symbols are rearranged into a matrix (v k,t ), using frequency domain differential modulation technology to represent information as the phase difference between two adjacent subcarrier signals in the same OFDM symbol;

[0010] Step 3: By analyzing the K subcarrier signals on each OFDM symbol Perform a K-point inverse discrete Fourier transform to convert the frequency domain sequence into a time domain transmission sequence. A cyclic prefix with a length equal to the number of channel paths is added to the time domain transmission sequence to combat the multipath effect of the channel. The parallel time domain transmission sequences with the cyclic prefix are then arranged into a serial sequence and sent to the receiver through the wireless channel.

[0011] Step 4: The receiver receives the serial sequence sent in step 3, arranges it into a parallel sequence and removes the cyclic prefix, and then calculates The K-point discrete Fourier transform is performed to obtain the received signals of the K subcarriers on the t-th OFDM symbol and detect the information by comparing the two consecutive received subcarrier signals on the same OFDM symbol. Then, the parallel detected signals are rearranged into a serial sequence and the detected data is converted into B-bit information bits through the M-order PSK soft decision demodulator and channel decoder. Finally, the receiver obtains a B-bit length estimated information bit sequence

[0012] As a further improvement of the present invention, in step 2, the signal of the kth subcarrier on the tth OFDM symbol is denoted as d k,t , expressed as

[0013] d k,t =v k,t d k-1,t

[0014] Among them, d 0,t =1 represents the initial reference signal of the tth OFDM symbol in the frequency domain differential OFDM. As a further improvement of the present invention, in step 3, the transmission sequence of the tth OFDM symbol including the cyclic prefix is ​​expressed as

[0015]

[0016] Where -L≤i≤K-1 represents the sampling point, and k represents the coefficient of the subcarrier. As a further improvement of the present invention, in step 4, assuming perfect symbol synchronization, s t The corresponding received signal of (i) after removing the cyclic prefix is

[0017]

[0018] Among them, 0≤i≤K-1, h t (l) represents the channel gain of the lth path during the tth OFDM symbol and w t (i) represents additive noise.

[0019] As a further improvement of the present invention, in step 4, the received signal on the k-th subcarrier of the t-th OFDM symbol is:

[0020]

[0021] As a further improvement of the present application, in the step 4, the receiver detects the information by comparing two consecutive subcarrier signals on the same OFDM symbol, thus the detected signal is represented as

[0022] The present application also discloses a frequency domain differential modulation system for high-reliability low-latency mobile communication, comprising a memory, a processor and a computer program stored in the memory, the computer program is configured to be called by the processor to realize the steps of the frequency domain differential modulation method of the present application.

[0023] The present application also discloses a computer readable storage medium, which stores a computer program, the computer program is configured to be called by a processor to realize the steps of the frequency domain differential modulation method of the present application.

[0024] The beneficial effects of the present application are that the frequency domain differential modulation method of the present application can realize high-reliability low-latency mobile communication with extremely low signaling cost and wireless resources. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the pilot symbol pattern specified in 3GPP Release 18 for mini-slot short packet transmission;

[0026] Figure 2 is the reference symbol pattern based on the frequency domain differential modulation technology of the present application;

[0027] Figure 3 is the system block diagram of the frequency domain differential modulation method of the present application. DETAILED DESCRIPTION

[0028] The application discloses a frequency domain differential modulation method for high-reliability and low-latency mobile communication, which is used for reducing channel estimation cost based on a mini-slot format in a high-reliability and low-latency mobile communication scene. A traditional short packet transmission scheme based on the mini-slot format adopts a pilot scheme to realize reliable channel estimation and data detection. However, considering that the data packet size of high-reliability and low-latency communication is small, the pilot symbol used for channel estimation will consume a considerable part of valuable signaling, time, bandwidth and power cost. To solve the above challenge, the application proposes a frequency domain differential modulation method for high-reliability and low-latency mobile communication to realize low-cost mini-slot short packet transmission. The frequency domain differential modulation technology can map the transmitted information into the phase difference of adjacent subcarrier signals under the same orthogonal frequency-division multiplexing (OFDM) symbol, and restore the required data by comparing the phase difference between two subcarrier signals, thereby avoiding the channel estimation process and greatly reducing the signaling cost.

[0029] The reference symbol pattern based on the frequency domain differential modulation technology proposed by the application is shown in Figure 2 As shown in Figure 2 , the frequency domain differential modulation technology only needs 2, 4 or 7 reference symbols to realize data detection under the mini-slot format. Therefore, compared with the pilot scheme, the frequency domain differential modulation technology can realize high-reliability and low-latency mobile communication with extremely low signaling cost and wireless resources.

[0030] The working mode of the frequency domain differential modulation method of the application is shown in Figure 3 The application considers a single-input single-output high-reliability and low-latency mobile communication system based on the mini-slot format with K subcarriers and T consecutive OFDM symbols. In addition, the application assumes that the transmitter has an urgent information bit sequence g={g1,g2,...,g B}, wherein B is the length of the sequence. Specifically, the domain differential modulation method comprises the following steps:

[0031] Step 1: In order to improve the reliability of the system, a channel encoder is adopted to convert B information bits into J coded bits.

[0032] Step 2: For a differential modulation OFDM system, first, the J coded bits are mapped into an M-order phase-shift keying (PSK) symbol block c={c1,c2,...,c N} with a length of N=J / log2M, wherein is the constellation alphabet of M-ary PSK symbols, and N is an integer. Next, N PSK symbols are rearranged into a (K-1) x T matrix (v k,t ). And the information is represented as the phase difference between two adjacent subcarrier signals in the same OFDM symbol using frequency domain differential modulation technique. Therefore, the signal of the kth subcarrier on the tth OFDM symbol, denoted as d k,t , can be expressed as

[0033] d k,t = v k,t d k-1,t

[0034] where d 0,t = 1 represents the initial reference signal of the tth OFDM symbol in frequency domain differential OFDM;

[0035] Step 3: Convert the frequency domain sequence to time domain transmission sequence by performing K-point inverse discrete Fourier transform (IDFT) on the K subcarrier signals d on each OFDM symbol, and add a cyclic prefix (CP) with the same length as the number of channel paths to the time domain transmission sequence to combat the multipath effect of the channel. Therefore, the transmission sequence of the tth OFDM symbol including the cyclic prefix can be expressed as

[0036]

[0037] where -L≤i≤K-1 represents the sampling point, k represents the coefficient of the subcarrier, e represents the natural exponential function exp(x), i.e., the exponential operation when performing inverse Fourier transform; then arrange the parallel time domain transmission sequence with cyclic prefix into a serial sequence, and finally send it to the receiver through the wireless channel.

[0038] Step 4: The receiver receives the serial sequence sent in step 3, arranges it into a parallel sequence, removes the cyclic prefix, and assumes perfect synchronization, s t (i) is the corresponding received signal after removing the cyclic prefix

[0039]

[0040] where 0≤i≤K-1 represents the sampling, h t (l) represents the channel gain of the lth path during the tth OFDM symbol, and w t (i) represents additive noise.

[0041] Then, the K-point discrete Fourier transform of r is calculated, and rt (i) represents the received signal, t represents the tth OFDM symbol, i represents the ith sample, and the received signal on the kth subcarrier of the tth OFDM symbol is obtained as:

[0042]

[0043] The detected signal can be represented as by comparing the received subcarrier signals of two consecutive subcarriers in the same OFDM symbol.

[0044]

[0045] Then, the parallel detected signals are rearranged into a serial sequence, and the detected data are converted into B-bit information bits by a M-order PSK soft decision demodulator and a channel decoder in sequence, and finally, the receiver can obtain a B-bit length estimated information bit sequence.

[0046] The application further discloses a frequency domain differential modulation system for high-reliability and low-latency mobile communication, which comprises a memory, a processor and a computer program stored in the memory.

[0047] The application further discloses a computer readable storage medium, which stores a computer program configured to realize the steps of the frequency domain differential modulation method when called by a processor.

[0048] The frequency domain differential modulation method can realize high-reliability and low-latency mobile communication with extremely low signaling cost and wireless resources.

[0049] The above is a further detailed description of the application in combination with specific preferred embodiments, and the specific implementation of the application cannot be limited to the description. For ordinary skilled persons in the technical field of the application, some simple deductions or replacements can be made without departing from the concept of the application, and all of them should be regarded as falling within the protection scope of the application.

Claims

1. A frequency domain differential modulation method for high-reliability and low-latency mobile communications, characterized in that: The following steps are involved: Step 1: The transmitter uses a channel encoder to convert B Converts information bits into J Bit encoding bits; Step 2: For differentially modulated OFDM systems, J The bit encoding bitmap is a length of of M Phase Shift Keying Symbol Block ,in , is the constellation alphabet of the M-order PSK symbol, and assumes N is an integer, N PSK symbols are rearranged into a Matrix , using frequency domain differential modulation technology to M The phase shift keying symbol block is represented as the phase difference between two adjacent subcarrier signals in the same OFDM symbol; Step 3: By analyzing the K subcarrier signals on each OFDM symbol Perform K-point inverse discrete Fourier transform to convert the frequency domain sequence into a time domain transmission sequence, and add a cyclic prefix with the same length as the number of channel paths to the time domain transmission sequence to combat the multipath effect of the channel. Arrange the parallel time domain transmission sequences with the cyclic prefix added into a serial sequence and send it to the receiver through the wireless channel, where k Indicates the index of the subcarrier; Step 4: The receiver receives the serial sequence sent in step 3, arranges it into a parallel sequence, removes the cyclic prefix, and calculates of K Point discrete Fourier transform, i Indicates the i samples, r t ( i ) for The corresponding received signal is the signal after removing the cyclic prefix, The first t OFDM symbol transmission sequence, get the t The received signals of K subcarriers on an OFDM symbol are compared with the two consecutive received subcarrier signals on the same OFDM symbol to detect the information, and the parallel detected signals are rearranged into a serial sequence and passed through M The PSK soft decision demodulator and channel decoder convert the detected data into B bit information bit, the receiver gets a B Bit length estimation information bit sequence .

2. The frequency domain differential modulation method according to claim 1, wherein: In step 2, t OFDM symbol k The signal of the subcarrier is recorded as , expressed as , in, Indicates the frequency domain differential OFDM t The initial reference signal of OFDM symbols.

3. The frequency domain differential modulation method according to claim 1, wherein: In step 3, the first t The transmission sequence of OFDM symbols is expressed as ， in, Indicates the sampling point.

4. The frequency domain differential modulation method according to claim 3, wherein: In step 4, assuming perfect symbol synchronization, The corresponding received signal after removing the cyclic prefix is , in, , Indicates the The path in t OFDM symbol period and represents additive noise.

5. The frequency domain differential modulation method according to claim 1, wherein: In step 4, t The first OFDM symbol k The received signal on the subcarrier is: 。 6. The frequency domain differential modulation method according to claim 1, wherein: In step 4, the receiver detects information by comparing two consecutive subcarrier signals on the same OFDM symbol. The detected signal is expressed as 。 7. A frequency domain differential modulation system for high-reliability and low-latency mobile communications, characterized in that: include: A memory, a processor, and a computer program stored in the memory, wherein the computer program is configured to implement the steps of the frequency domain differential modulation method according to any one of claims 1 to 6 when called by the processor.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program is configured to implement the steps of the frequency domain differential modulation method according to any one of claims 1 to 6 when called by a processor.

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