Frequency domain differential modulation method and system for high-reliability and low-delay mobile communication, and storage medium

Abstract

The invention provides a frequency domain differential modulation method and system for high-reliability and low-delay mobile communication, and a storage medium. The frequency domain differential modulation method comprises the following steps: step 1, converting B-bit information bits into J-bit coded bits; 2, mapping J coding bits into an M-order phase shift keying symbol block, and expressing information as a phase difference of two adjacent subcarrier signals in the same OFDM symbol by using a frequency domain differential modulation technology; step 3, executing K-point inverse discrete Fourier transform to convert the frequency domain transmission sequence into a time domain transmission sequence, and adding a cyclic prefix in the time domain transmission sequence; and 4, receiving the serial sequence by a receiver, calculating K-point discrete Fourier transform of # imgabs0 #, detecting data by comparing subcarrier signals on the same OFDM symbol, and converting the data into B-bit information bits by using a phase shift keying soft demodulator and a channel decoder. The method has the beneficial effects that high-reliability and low-delay mobile communication can be realized with extremely low signaling cost and wireless resources.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a frequency domain differential modulation method, system and storage medium for high-reliability and low-latency mobile communications. Background Art

[0002] Ultra-reliable and low-latency communications (URLLC) is the main application scenario of the fifth generation (5G) and sixth generation (6G) wireless communication networks, which can realize various mission-critical applications such as factory automation, remote surgery, tactile Internet and autonomous driving. To support these applications, the standardization organization 3GPP (3rd generation partnership project) specifies performance requirements of 1 millisecond physical layer latency and 99.999% reliability for ultra-reliable and low-latency applications under 5G networks. As emerging services have increasingly stringent requirements on network performance, it is expected that the physical layer latency and reliability requirements of ultra-reliable and low-latency communications in the upcoming 6G network will reach 0.1ms and 99.99999%, respectively.

[0003] In order to meet such stringent performance requirements in highly reliable and low-latency communications, 3GPP introduced a new feature of mini-slot for 5G networks. Specifically, mini-slot uses a group of 2, 4, or 7 OFDM symbols as the basic unit for data scheduling and resource allocation. In contrast, the minimum scheduling unit for the other two major use cases in 5G networks, namely enhanced mobile broadband (eMBB) and massive machine-type communications (mMTC), is a traditional time slot occupying 12 or 14 OFDM symbols. In the traditional time slot format, data packets arriving within the time slot must wait until the end of the time slot before they can be transmitted. In contrast, the mini-slot format with finer time domain division can start data transmission at any OFDM symbol without waiting for the time 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 achieve 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 the channel estimation performance, such as Figure 1 (d) as shown.

[0005] Depend on Figure 1 (a) It can be seen that in 2 OFDM symbol units, up to 25% of the wireless resources are allocated to pilot symbols for channel estimation, which is very expensive for short packet transmission and significantly damages the system's delay performance and spectrum efficiency. On the other hand, reducing the proportion of pilot symbols will lead to a decrease in channel estimation accuracy, thereby seriously reducing the performance of data detection, especially in high mobility scenarios with rapid channel fluctuations. 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 of 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-delay mobile communication, 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) of size (K-1)×T 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 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. Then, arrange the parallel time domain transmission sequences with the cyclic prefix added into a serial sequence, and finally send it 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 signal of K subcarriers on the t-th OFDM symbol and detect the information by comparing 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 the 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 invention, in step 4, the receiver detects information by comparing two consecutive subcarrier signals on the same OFDM symbol. Therefore, the detected signal is expressed as

[0022] The present invention also discloses a frequency domain differential modulation system for high-reliability and low-latency mobile communications, comprising: a memory, a processor, and a computer program stored on the memory, wherein the computer program is configured to implement the steps of the frequency domain differential modulation method of the present invention when called by the processor.

[0023] The present invention also discloses a computer-readable storage medium, wherein 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 of the present invention when called by a processor.

[0024] The beneficial effect of the present invention is that the frequency domain differential modulation method of the present invention can realize high-reliability and low-delay mobile communication with extremely low signaling cost and wireless resources. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 2 It is a reference symbol mode based on the frequency domain differential modulation technology of the present invention;

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

[0028] The present invention discloses a frequency domain differential modulation method for high-reliability and low-latency mobile communications, which is used to reduce the channel estimation cost based on the mini-slot format in the high-reliability and low-latency mobile communication scenario. Traditional short packet transmission based on the mini-slot format adopts a pilot scheme to achieve reliable channel estimation and data detection. However, considering that the data packet size of high-reliability and low-latency communications is small, the pilot symbols used for channel estimation will consume a considerable amount of precious signaling, time, bandwidth and power costs. To address the above challenges, the present invention proposes a frequency domain differential modulation method for high-reliability and low-latency mobile communications to achieve low-cost mini-slot short packet transmission. Frequency domain differential modulation technology can map the transmitted information to the phase difference of adjacent subcarrier signals under the same orthogonal frequency division multiplexing (OFDM) symbol, and recover the required data by comparing the phase between the two subcarrier signals, thereby avoiding the channel estimation process and greatly reducing the signaling cost.

[0029] The reference symbol mode based on frequency domain differential modulation technology proposed in the present invention is as follows: Figure 2 As shown. Figure 2 It can be seen that frequency domain differential modulation technology only needs 2, 4 or 7 reference symbols to achieve data detection in the mini-slot format. Therefore, compared with the pilot scheme, frequency domain differential modulation technology can achieve high-reliability and low-latency mobile communications with extremely low signaling costs and wireless resources.

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

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

[0032] Step 2: For the differentially modulated OFDM system, first map the J coded bits into an M-order phase-shift keying (PSK) symbol block c = {c1, c2, ..., c N},in is the constellation alphabet of the M-order PSK symbol, and assumes that N is an integer. Next, the N PSK symbols are rearranged into a matrix (v k,t ). The frequency domain differential modulation technique is used to represent the information as the phase difference between two adjacent subcarrier signals in the same OFDM symbol. Therefore, the signal of the kth subcarrier on the tth OFDM symbol is denoted by d k,t , which can be expressed as

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

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

[0035] Step 3: By analyzing the K subcarrier signals on each OFDM symbol K-point inverse discrete Fourier transform (IDFT) is performed to convert the frequency domain sequence into a time domain transmission sequence, and a cyclic prefix (CP) with a length consistent with the number of channel paths is added to the time domain transmission sequence to combat the multipath effect of the channel. Therefore, the transmission sequence of the t-th OFDM symbol, including the cyclic prefix, can be expressed as

[0036]

[0037] Among them, -L≤i≤K-1 represents the sampling point, k represents the coefficient of the subcarrier, and e represents the natural exponential function exp(x), that is, the exponential operation during the inverse Fourier transform; then the parallel time domain transmission sequence with the cyclic prefix added is arranged into a serial sequence, and finally sent 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 and removes the cyclic prefix. Assuming perfect symbol synchronization, s t The corresponding received signal of (i) after removing the cyclic prefix is

[0039]

[0040] Among them, 0≤i≤K-1 represents 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, by calculating The K-point discrete Fourier transform oft (i) represents the received signal, t represents the t-th OFDM symbol, i represents the ith sample, and the received signal on the k-th subcarrier of the t-th OFDM symbol is:

[0042]

[0043] The information is detected by comparing the received subcarrier signals of two consecutive subcarriers on the same OFDM symbol. Therefore, the detected signal can be expressed as

[0044]

[0045] 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 the channel decoder. Finally, the receiver can obtain a B-bit length estimated information bit sequence.

[0046] The present invention also discloses a frequency domain differential modulation system for high-reliability and low-latency mobile communications, comprising: a memory, a processor, and a computer program stored on the memory, wherein the computer program is configured to implement the steps of the frequency domain differential modulation method of the present invention when called by the processor.

[0047] The present invention also discloses a computer-readable storage medium, wherein 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 of the present invention when called by a processor.

[0048] The beneficial effect of the present invention is that the frequency domain differential modulation method of the present invention can realize high-reliability and low-delay mobile communication with extremely low signaling cost and wireless resources.

[0049] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

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 information bits into J coded bits; 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) of size (K-1)×T 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; 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. Then, arrange the parallel time domain transmission sequences with the cyclic prefix added into a serial sequence, and finally send it to the receiver through the wireless channel. 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 signal of K subcarriers on the t-th OFDM symbol and detect the information by comparing 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 the channel decoder. Finally, the receiver obtains a B-bit length estimated information bit sequence.

2. The frequency domain differential modulation method according to claim 1, characterized in that: In step 2, the signal of the kth subcarrier on the tth OFDM symbol is denoted as d k,t , expressed as d k,t =v k,t d k-1,t Among them, d 0,t =1 represents the initial reference signal of the tth OFDM symbol in frequency domain differential OFDM.

3. The frequency domain differential modulation method according to claim 1, characterized in that: In step 3, the transmission sequence of the tth OFDM symbol including the cyclic prefix is ​​expressed as Among them, -L≤i≤K-1 represents the sampling point, and k represents the coefficient of the subcarrier.

4. The frequency domain differential modulation method according to claim 1, characterized in that: In step 4, assuming perfect symbol synchronization, s t The corresponding received signal of (i) after removing the cyclic prefix is 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.

5. The frequency domain differential modulation method according to claim 1, characterized in that: In step 4, the received signal on the k-th subcarrier of the t-th OFDM symbol is:

6. The frequency domain differential modulation method according to claim 1, characterized in that: In step 4, the receiver detects information by comparing two consecutive subcarrier signals on the same OFDM symbol. Therefore, 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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