Digital front-haul method and system based on non-uniformly protected coding modulation

Abstract

The application provides a digital front-haul method and system based on non-uniform protection coding modulation, comprising the following steps: S1, converting a continuous orthogonal frequency division multiplexing waveform into a quantized bit sequence, combining the quantized bit sequence according to importance, and coding; the coded bit block is mapped to a corresponding position of a symbol according to a preset mapping rule to obtain a symbol sequence, and the symbol sequence is converted into an optical signal and sent into an optical fiber; S2, receiving the optical signal, converting the optical signal into a symbol sequence, demodulating the symbol sequence to obtain a bit sequence, inversely mapping the bit sequence into a bit block according to a preset mapping rule, separately decoding the bit block, and recombining the decoded bit block to obtain a quantized bit sequence, and then recovering an orthogonal frequency division multiplexing signal. Compared with a traditional scheme, the signal quality is greatly improved at the same complexity.

Description

Technical Field

[0001] This invention relates to the field of fiber optic and wireless converged fronthaul technology, and more specifically, to a digital fronthaul method and system based on non-uniform protection coding modulation. Background Technology

[0002] Cloud Radio Access Network (C-RAN) offers a promising solution to the challenges of dense cell deployments. In C-RAN, the Baseband Unit (BBU) is separated from and integrated with the base station, while Remote Radio Units (RRUs) are distributed across each cell, providing interfaces for the antenna array. This network architecture offers numerous advantages, such as flexible resource allocation and lower implementation costs for coordinating multiple points. The link between the BBU and RRU is defined as fronthaul. There are two main fiber-based fronthaul implementations: Analog Radio over Fiber (A-RoF) and Digital Radio over Fiber (D-RoF). A-RoF offers high spectral efficiency but is susceptible to link impairments. D-RoF quantizes the radio signal into bits, making it unaffected by link distortion. Therefore, D-RoF can maintain signal fidelity while consuming bandwidth. With the advent of massive MIMO and the application of multiple spectrums in 5G scenarios, fronthaul data transmission rates are growing exponentially. Therefore, designing a fronthaul system with low complexity, high speed, and high fidelity has become a significant challenge for base station deployment.

[0003] The November 2017 issue of the journal "Journal of Lightwave Technology" (pages 4714-4720) disclosed a "Mobile Digital Fronthaul Method with Adaptive Digitization and Variable Channel Coding." This method enhances signal quality at the same data rate by adjusting the resolution of the ADC and simultaneously adjusting the coding redundancy of high-order and low-order bits. However, the ADC resolution and coding redundancy vary under different channel conditions, making practical implementation difficult and thus not completely solving the aforementioned technical problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a digital fronthaul method and system based on non-uniform protection coding modulation.

[0005] A digital fronthaul method based on non-uniform protection coding modulation provided by the present invention includes:

[0006] Step S1: Convert the continuous orthogonal frequency division multiplexing waveform into a quantized bit sequence, arrange and combine the quantized bit sequence according to importance, and encode it. The encoded bit blocks are mapped to the corresponding positions of the symbols according to the preset mapping rules to obtain the symbol sequence. The symbol sequence is converted into an optical signal and sent into the optical fiber.

[0007] Step S2: Receive the optical signal and convert it into a symbol sequence. Demodulate the symbol sequence to obtain a bit sequence. Reverse map the bit sequence into bit blocks according to a preset mapping rule. Decode each bit block individually and rearrange and combine the decoded bit blocks to obtain a quantized bit sequence, thereby recovering the orthogonal frequency division multiplexing signal.

[0008] Preferably, step S1 employs:

[0009] Step S1.1: Sample, quantize, and encode the continuous orthogonal frequency division multiplexing waveform to obtain a quantized bit sequence; then scramble the quantized bit sequence;

[0010] Step S1.2: Encode the scrambled quantized bit sequence according to its importance, map it according to a preset bit mapping rule, and modulate it to obtain a symbol sequence;

[0011] Step S1.3: Perform digital signal processing on the symbol sequence to obtain an electrical signal;

[0012] Step S1.4: Perform electro-optic conversion on the electrical signal to generate an optical signal and transmit it into the optical fiber.

[0013] Preferably, step S1.2 employs the following:

[0014] Step S1.2.1: Arrange the obtained quantized bit sequence according to importance, and group bits with the same importance into the same bit block;

[0015] Step S1.2.2: Perform FEC encoding on different bit blocks to obtain encoded bit sequences;

[0016] Step S1.2.3: Map the encoded bit sequence to different bit positions of the quadrature amplitude modulation symbol according to their importance.

[0017] Preferably, step S1.2.3 involves mapping more important bit sequences to more reliable bit positions of symbols.

[0018] Preferably, step S2 employs:

[0019] Step S2.1: Receive the optical signal, convert the optical signal into an electrical signal through a photodiode, and then perform digital signal processing on the electrical signal to obtain a noisy symbol sequence;

[0020] Step S2.2: After demodulating and decoding the symbol sequence to obtain the bit sequence, the bit sequence is reverse-mapped according to the preset bit mapping rule to obtain the recovered quantized bit sequence;

[0021] Step S2.3: Descramble the quantized bit sequence, and then perform inverse quantization to obtain the orthogonal frequency division multiplexing signal.

[0022] Preferably, step S2.2 employs the following:

[0023] Step S2.2.1: Calculate the maximum likelihood ratio for each bit on each symbol, and then input the maximum likelihood ratio into the decoder to obtain the decoded bit sequence;

[0024] Step S2.2.2: Rearrange the bit sequence, mapping each bit in the bit block to the corresponding quantized bit position.

[0025] A digital fronthaul system based on non-uniform guard coded modulation provided by the present invention includes:

[0026] Module M1: Converts continuous orthogonal frequency division multiplexing waveforms into quantized bit sequences, arranges and combines the quantized bit sequences according to importance, encodes them, maps the encoded bit blocks to the corresponding positions of symbols according to preset mapping rules to obtain symbol sequences, and converts the symbol sequences into optical signals and sends them into optical fibers;

[0027] Module M2: Receives optical signals and converts them into symbol sequences. It demodulates the symbol sequences to obtain bit sequences, and then maps the bit sequences back into bit blocks according to a preset mapping rule. It decodes the bit blocks individually and rearranges and combines the decoded bit blocks to obtain quantized bit sequences, thereby recovering the orthogonal frequency division multiplexing signal.

[0028] Preferably, module M1 adopts:

[0029] Module M1.1: Samples, quantizes, and encodes continuous orthogonal frequency division multiplexing waveforms to obtain a quantized bit sequence; then scrambles the quantized bit sequence.

[0030] Module M1.2: Encodes the scrambled quantized bit sequence according to importance, maps and modulates it according to a preset bit mapping rule, and obtains a symbol sequence;

[0031] Module M1.3: Performs digital signal processing on symbol sequences to obtain electrical signals;

[0032] Module M1.4: Converts electrical signals into optical signals through electro-optical conversion and transmits them into the optical fiber;

[0033] The module M1.2 adopts:

[0034] Module M1.2.1: Arranges the obtained quantized bit sequence according to importance, and bits with the same importance are grouped into the same bit block;

[0035] Module M1.2.2: Perform FEC encoding on different bit blocks to obtain encoded bit sequences;

[0036] Module M1.2.3: Maps the coded bit sequence to different bit positions of the quadrature amplitude modulation symbol according to their importance;

[0037] The module M1.2.3 employs the following approach: mapping more important bit sequences to more reliable bit positions of symbols.

[0038] Preferably, the module M2 adopts:

[0039] Module M2.1: Receives optical signals, converts them into electrical signals through a photodiode, and then performs digital signal processing on the electrical signals to obtain a noisy symbol sequence;

[0040] Module M2.2: After demodulating and decoding the symbol sequence to obtain the bit sequence, the bit sequence is reverse-mapped according to the preset bit mapping rules to obtain the recovered quantized bit sequence;

[0041] Module M2.3: Descrambles and quantizes the bit sequence, then performs inverse quantization to obtain the orthogonal frequency division multiplexed signal.

[0042] Preferably, module M2.2 adopts:

[0043] Module M2.2.1: Calculates the maximum likelihood ratio for each bit on each symbol, and then inputs the maximum likelihood ratio into the decoder to obtain the decoded bit sequence;

[0044] Module M2.2.2: Rearranges the bit sequence, mapping each bit in the bit block to the corresponding quantized bit position.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. This invention is based on non-uniform protection coding modulation. By rearranging the quantized bit sequence of the OFDM signal to obtain bit blocks, each bit block is encoded separately, thereby preserving the information of bit importance.

[0047] 2. Based on the importance of bits, this invention maps different encoded bit blocks to different positions in the 64QAM symbol, that is, more important bit sequences are mapped to more reliable bit positions;

[0048] 3. By adopting the digital fronthaul method based on non-uniform protection coding modulation described in this invention, the purpose of protecting important bits is achieved, thereby enhancing signal quality;

[0049] 4. The key features of this invention are the bit rearrangement before encoding and the bit mapping before modulation. It is simple to implement, has low complexity, and can improve the overall system performance, overcoming the shortcomings of existing technologies. Attached Figure Description

[0050] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0051] Figure 1 This is a flowchart of the digital fronthaul method and system based on non-uniform protection coding modulation of the present invention;

[0052] Figure 2 This is a detailed diagram illustrating the process of rearranging and mapping the quantized bit sequence in this invention;

[0053] Figure 3 This is a schematic diagram showing the mapping relationship between 64QAM symbols and bits used in this invention;

[0054] Figure 4 This is a schematic diagram illustrating the performance of the present invention applied to a digital fronthaul simulation system. Detailed Implementation

[0055] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0056] Example 1

[0057] According to the present invention, a digital fronthaul method based on non-uniform protection code modulation is provided, such as... Figures 1 to 4 As shown, it includes:

[0058] Step S1: Convert the continuous orthogonal frequency division multiplexing waveform into a quantized bit sequence, arrange and combine the quantized bit sequence according to importance, and encode it. The encoded bit blocks are mapped to the corresponding positions of the symbols according to the preset mapping rules to obtain the symbol sequence. The symbol sequence is converted into an optical signal and sent into the optical fiber.

[0059] Step S2: Receive the optical signal and convert it into a symbol sequence. Demodulate the symbol sequence to obtain a bit sequence. Reverse map the bit sequence into bit blocks according to a preset mapping rule. Decode each bit block individually and rearrange and combine the decoded bit blocks to obtain a quantized bit sequence, thereby recovering the orthogonal frequency division multiplexing signal.

[0060] This invention rearranges and combines bits according to their importance, and then maps the high-order bits to more reliable bit positions in Quadrature Amplitude Modulation (QAM) symbols, thereby improving signal quality.

[0061] Specifically, step S1 employs the following:

[0062] Step S1.1: Sample, quantize, and encode the continuous orthogonal frequency division multiplexing waveform to obtain a quantized bit sequence; then scramble the quantized bit sequence;

[0063] Step S1.2: Encode the scrambled quantized bit sequence according to its importance, map it according to the preset bit mapping rules, and modulate it to obtain a symbol sequence; wherein, before encoding the bit sequence, the bit sequence is rearranged to ensure that the encoded bit sequence still retains the original information about importance.

[0064] Step S1.3: Perform digital signal processing (DSP) on the symbol sequence to obtain an electrical signal;

[0065] Step S1.4: Perform electro-optical conversion (E / O) processing on the electrical signal to generate an optical signal and transmit it into the optical fiber.

[0066] Specifically, step S1.2 employs the following:

[0067] Step S1.2.1: Arrange the obtained quantized bit sequence according to importance, and group bits with the same importance into the same bit block;

[0068] Step S1.2.2: Encode different bit blocks using FEC to obtain encoded bit sequences; where FEC and specific modulation schemes are independent of the design of this method and can be changed within a reasonable range.

[0069] Step S1.2.3: Map the encoded bit sequence to different bit positions of the quadrature amplitude modulation (QAM) symbol according to its importance. That is, the bit blocks with higher importance are mapped to more reliable bit positions on the symbol to obtain the corresponding symbol sequence.

[0070] Specifically, step S1.2.3 involves mapping more important bit sequences to more reliable bit positions of symbols.

[0071] Specifically, step S2 employs the following:

[0072] Step S2.1: Receive the optical signal and convert it into an electrical signal by photoelectric conversion (O / E) through a photodiode (PD). Then, perform digital signal processing (DSP) on the electrical signal to obtain a noisy symbol sequence.

[0073] Step S2.2: After demodulating and decoding the symbol sequence to obtain the bit sequence, the bit sequence is reverse-mapped according to the preset bit mapping rule to obtain the recovered quantized bit sequence;

[0074] Step S2.3: Descramble the quantized bit sequence and then perform inverse quantization to obtain the orthogonal frequency division multiplexing (OFDM) signal.

[0075] Specifically, step S2.2 employs the following:

[0076] Step S2.2.1: Calculate the maximum likelihood ratio for each bit on each symbol, and then input the maximum likelihood ratio into the decoder to obtain the decoded bit sequence;

[0077] Step S2.2.2: Rearrange the bit sequence, mapping the bits in each bit block to the corresponding quantization bit positions. The bits of the first bit block are mapped to the first bit of all OFDM quantization bit sequences, the bits of the second bit block are mapped to the second bit of all OFDM quantization bit sequences, and so on.

[0078] A digital fronthaul system based on non-uniform guard coded modulation provided by the present invention includes:

[0079] Module M1: Converts continuous orthogonal frequency division multiplexing waveforms into quantized bit sequences, arranges and combines the quantized bit sequences according to importance, encodes them, maps the encoded bit blocks to the corresponding positions of symbols according to preset mapping rules to obtain symbol sequences, and converts the symbol sequences into optical signals and sends them into optical fibers;

[0080] Module M2: Receives optical signals and converts them into symbol sequences. It demodulates the symbol sequences to obtain bit sequences, and then maps the bit sequences back into bit blocks according to a preset mapping rule. It decodes the bit blocks individually and rearranges and combines the decoded bit blocks to obtain quantized bit sequences, thereby recovering the orthogonal frequency division multiplexing signal.

[0081] Specifically, module M1 adopts:

[0082] Module M1.1: Samples, quantizes, and encodes continuous orthogonal frequency division multiplexing waveforms to obtain a quantized bit sequence; then scrambles the quantized bit sequence.

[0083] Module M1.2: Encodes the scrambled quantized bit sequence according to importance, maps and modulates it according to a preset bit mapping rule to obtain a symbol sequence; before encoding the bit sequence, the bit sequence is rearranged to ensure that the encoded bit sequence still retains the original information about importance.

[0084] Module M1.3: Performs digital signal processing (DSP) on the symbol sequence to obtain an electrical signal;

[0085] Module M1.4: Performs electro-optical conversion (E / O) on electrical signals to generate optical signals and transmits them into optical fibers.

[0086] Specifically, module M1.2 adopts:

[0087] Module M1.2.1: Arranges the obtained quantized bit sequence according to importance, and bits with the same importance are grouped into the same bit block;

[0088] Module M1.2.2: FEC is applied to different bit blocks to obtain encoded bit sequences; the FEC and specific modulation scheme are independent of the design of this method and can be changed within a reasonable range.

[0089] Module M1.2.3: Maps the encoded bit sequence to different bit positions on the quadrature amplitude modulation (QAM) symbol according to its importance. That is, the bit blocks with higher importance are mapped to more reliable bit positions on the symbol, thus obtaining the corresponding symbol sequence.

[0090] Specifically, module M1.2.3 employs the following approach: mapping more important bit sequences to more reliable bit positions of symbols.

[0091] Specifically, module M2 adopts:

[0092] Module M2.1: Receives optical signals and converts them into electrical signals through photodiodes (PDs) to form electrical signals. Then, it performs digital signal processing (DSP) on the electrical signals to obtain a noisy symbol sequence.

[0093] Module M2.2: After demodulating and decoding the symbol sequence to obtain the bit sequence, the bit sequence is reverse-mapped according to the preset bit mapping rules to obtain the recovered quantized bit sequence;

[0094] Module M2.3: Descrambles and quantizes the bit sequence, then performs inverse quantization to obtain the orthogonal frequency division multiplexing (OFDM) signal.

[0095] Specifically, module M2.2 adopts:

[0096] Module M2.2.1: Calculates the maximum likelihood ratio for each bit on each symbol, and then inputs the maximum likelihood ratio into the decoder to obtain the decoded bit sequence;

[0097] Module M2.2.2: Rearranges the bit sequence, mapping the bits in each bit block to the corresponding quantized bit positions. The bits of the first bit block are mapped to the first bit of all OFDM quantized bit sequences, the bits of the second bit block are mapped to the second bit of all OFDM quantized bit sequences, and so on.

[0098] This invention also discloses a detailed method for rearranging bits and a bit mapping method based on 64QAM. The bit mapping method is related to the specific mapping relationship between QAM symbols and bits. In the examples of this invention, a relatively common Gray mapping is used between bits and QAM symbols, with different bits having different reliability. Each symbol in 64QAM has 6 bits, and the reliability order is: (first bit = fourth bit) > (second bit = fifth bit) > (third bit = sixth bit).

[0099] The present invention also provides simulation analysis of a digital fronthaul method and system based on non-uniform guard coded modulation, such as... Figure 4 As shown in the figure, Bit-Interleaved Coded Modulation (BICM) refers to the traditional scheme, while Uniform Error Protection Coded Modulation (UEP-CM) is the method of this invention. The Signal-to-Noise Ratio (SNR) gain represents the gain achieved by the method of this invention compared to the traditional method. In the simulation example, the FEC used is Low-Density Parity-Check (LDPC) coding with a code rate of 5 / 6 and 3 iterations. The results show that, using the same number of iterations and code rate for FEC, this method achieves a gain greater than 15dB compared to the traditional scheme.

[0100] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0101] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A digital fronthaul method based on non-uniform guard coded modulation, characterized in that, include: Step S1: Convert the continuous orthogonal frequency division multiplexing waveform into a quantized bit sequence, arrange and combine the quantized bit sequence according to importance, and encode it. The encoded bit blocks are mapped to the corresponding positions of the symbols according to the preset mapping rules to obtain the symbol sequence. The symbol sequence is converted into an optical signal and sent into the optical fiber. Step S2: Receive the optical signal and convert it into a symbol sequence. Demodulate the symbol sequence to obtain a bit sequence. Map the bit sequence back into bit blocks according to a preset mapping rule. Decode the bit blocks individually and rearrange and combine the decoded bit blocks to obtain a quantized bit sequence, thereby recovering the orthogonal frequency division multiplexing signal. Step S1 adopts the following: Step S1.1: Sample, quantize, and encode the continuous orthogonal frequency division multiplexing waveform to obtain a quantized bit sequence; then scramble the quantized bit sequence; Step S1.2: Encode the scrambled quantized bit sequence according to its importance, map it according to a preset bit mapping rule, and modulate it to obtain a symbol sequence; Step S1.3: Perform digital signal processing on the symbol sequence to obtain an electrical signal; Step S1.4: Perform electro-optic conversion on the electrical signal to generate an optical signal and transmit it into the optical fiber; Step S1.2 adopts the following: Step S1.2.1: Arrange the obtained quantized bit sequence according to importance, and group bits with the same importance into the same bit block; Step S1.2.2: Perform FEC encoding on different bit blocks to obtain encoded bit sequences; Step S1.2.3: Map the encoded bit sequence to different bit positions of the quadrature amplitude modulation symbol according to their importance; Step S1.2.3 involves mapping the more important bit sequence to the bit position of the symbol that is more reliable; Step S2 employs the following: Step S2.1: Receive the optical signal, convert the optical signal into an electrical signal through a photodiode, and then perform digital signal processing on the electrical signal to obtain a noisy symbol sequence; Step S2.2: After demodulating and decoding the symbol sequence to obtain the bit sequence, the bit sequence is reverse-mapped according to the preset bit mapping rule to obtain the recovered quantized bit sequence; Step S2.3: Descramble the quantized bit sequence, and then perform inverse quantization to obtain the orthogonal frequency division multiplexed signal; Step S2.2 adopts the following: Step S2.2.1: Calculate the maximum likelihood ratio for each bit on each symbol, and then input the maximum likelihood ratio into the decoder to obtain the decoded bit sequence; Step S2.2.2: Rearrange the bit sequence, mapping each bit in the bit block to the corresponding quantized bit position.

2. A digital fronthaul system based on non-uniform protection code modulation, characterized in that, include: Module M1: Converts continuous orthogonal frequency division multiplexing waveforms into quantized bit sequences, arranges and combines the quantized bit sequences according to importance, encodes them, maps the encoded bit blocks to the corresponding positions of symbols according to preset mapping rules to obtain symbol sequences, and converts the symbol sequences into optical signals and sends them into optical fibers; Module M2: Receives optical signals and converts them into symbol sequences. It demodulates the symbol sequences to obtain bit sequences, and then maps the bit sequences back into bit blocks according to a preset mapping rule. It decodes the bit blocks individually and rearranges and combines the decoded bit blocks to obtain quantized bit sequences, thereby recovering the orthogonal frequency division multiplexing signal. The module M1 adopts: Module M1.1: Samples, quantizes, and encodes continuous orthogonal frequency division multiplexing waveforms to obtain a quantized bit sequence; then scrambles the quantized bit sequence. Module M1.2: Encodes the scrambled quantized bit sequence according to importance, maps and modulates it according to a preset bit mapping rule, and obtains a symbol sequence; Module M1.3: Performs digital signal processing on symbol sequences to obtain electrical signals; Module M1.4: Converts electrical signals into optical signals through electro-optical conversion and transmits them into the optical fiber; The module M1.2 adopts: Module M1.2.1: Arranges the obtained quantized bit sequence according to importance, and bits with the same importance are grouped into the same bit block; Module M1.2.2: Perform FEC encoding on different bit blocks to obtain encoded bit sequences; Module M1.2.3: Maps the coded bit sequence to different bit positions of the quadrature amplitude modulation symbol according to their importance; The module M1.2.3 employs the following approach: mapping more important bit sequences to more reliable bit positions of the symbols; The module M2 adopts: Module M2.1: Receives optical signals, converts them into electrical signals through a photodiode, and then performs digital signal processing on the electrical signals to obtain a noisy symbol sequence; Module M2.2: After demodulating and decoding the symbol sequence to obtain the bit sequence, the bit sequence is reverse-mapped according to the preset bit mapping rules to obtain the recovered quantized bit sequence; Module M2.3: Descrambles and quantizes the bit sequence, then performs inverse quantization to obtain the orthogonal frequency division multiplexed signal; The module M2.2 adopts: Module M2.2.1: Calculates the maximum likelihood ratio for each bit on each symbol, and then inputs the maximum likelihood ratio into the decoder to obtain the decoded bit sequence; Module M2.2.2: Rearranges the bit sequence, mapping each bit in the bit block to the corresponding quantized bit position.

Images