Bit-rate Coding Research Articles

Photonic generation and programmable switching of variable-band chirped waveforms with immunity to power fading.

A photonic approach for generating and programmable switching variable-band chirped waveforms by using a dual-parallel Mach-Zehnder modulator (DPMZM) is proposed and experimentally demonstrated. By coupling binary switching codes with the baseband chirped signal and applying them into the RF input port of DPMZM, the variable-band chirped waveforms can be generated and fast switched. The switching speed is consistent with the input code bit rate. Moreover, by properly adjusting the bias voltages, the generated signals can be anti-dispersion transmitted over different distances. Full experimental verification on the generation and programmable switching of the chirped waveforms centered at 2.1, 6.3, and 8.4 GHz or 1.5, 4.5, and 6 GHz over 10 or 20 km standard single-mode fibers with 4 or 100 Mbps switching rates are successfully carried out. The proposed approach features compact architecture, programmable switching capability and immunity to power fading, which are significant in distributed multifunction radar networks with optical fiber-based transmission.

Enhanced voice over 5G transmission with unequal error protection and generative adversarial networks

SummaryVoice services have progressed significantly since the launch of mobile phones and have evolved from analog technology to digital ones. Since the launch of 5G, voice over 5G (Vo5G) will slowly take over legacy mobile technologies to provide better voice services. Nevertheless, interruptions and noise will continue to affect speech communication over wireless networks, ensuing in a reduced Quality of Service (QoS). Three enhanced transmission schemes for Vo5G are proposed. The first proposal benefits from the difference in weight of the bits of internet Low Bitrate Code (iLBC) coded packets to offer them diverse degrees of protection i.e. Unequal Error Protection (UEP). UEP enhances the reception quality by allowing the more significant bits to be decoded with greater reliability during 5G transmission. The second and third schemes substitute the usual Quadrature Amplitude Modulation (QAM) constellation with a Statistical QAM (SQAM) one. The second scheme arranges the significant bits on the SQAM constellation and the remaining bits onto the conventional QAM arrangement. For the third scheme, all the bits are arranged on the SQAM constellation. Generative Adversarial Networks (GAN) were incorporated into the third scheme as the third scheme provided better gains over the first and second schemes. GAN was used to synthesize and enhance parts of the speech file that were lost during transmission over the 5G channel resulting in a gain in Segmented Signal to Noise Ratio (SSNR). The addition of GAN boosted the gain obtained by the third scheme by 1.45 dB with 16‐QAM at a code rate of 1/3.

Polar code-based secure transmission with higher message rate combining channel entropy and computational entropy

The existing physical layer security schemes, which are based on the key generation model and the wire-tap channel model, achieve security by utilizing channel reciprocity entropy and noise entropy, respectively. In contrast, we propose a novel secure transmission framework that combines noise entropy with reciprocity entropy, achieved by inserting reciprocity entropy into the frozen bits of polar codes. Note that in real-world scenarios, when eavesdroppers employ polynomial-time attacks, the bit error rate (BER) increases due to the introduction of computational entropy. To achieve indistinguishability security, we convert the practical physical layer security metric, BER, into the average min-entropy, a widely accepted concept in cryptography. The simulation results demonstrate that the eavesdropper’s BER can be significantly increased without compromising the communication performance of the legitimate receiver. Under concrete parameters we selected, when compared to the joint scheme of physical layer key generation and one time pad, the modular semantically-secure scheme based on the wire-tap channel model, and the simple channel entropy combination scheme, our scheme achieves a message rate approximately 1.2 times, 3.8 times, and 1.4 times better, respectively. Experimental testing validates the feasibility of our scheme.

Вопрос о качественной определенности бита в естественном и искусственном интеллекте

Introduction. Advances in digital technology lead to the tendency to adjust the modern education system under the algorithms of artificial intelligence. In this regard the special relevance is acquired by a research of those aspects of human thinking which are not amenable to modeling in artificial intelligence systems. Theoretical analysis. In the concepts of the XX–XXI centuries eidos is transformed into a dynamic pattern. Patterns, unlike eidos-forms of ancient philosophy, fix not a static, but a dynamic form of a reproducible motion configuration. Patterns, like Plato’s eidos, are indivisible integrities that are not reduced to discrete elements of discourse. It is justified that the eidos configurations are formed not at the macro level of the gestalt, but at the micro level of the bit. The primary “not indifferent differences” of the bits of human intelligence are modifications of the initial organism dichotomy “organism – environment” (“inside – outside”, “inclusion in – ejection from”), differing from the bits of the binary code (1–0) of digital technology. Conclusion. It is concluded that the basic gestalts of creative thinking (“figure – background”) is not a secondary “emergent” quality of integrative integrity, but an elementary and irreducible “primary quality” of human intelligence bits.

Secure RoF system based on key nested polar code and feedback neural network.

With the development of 6 G network, the issue of information security is becoming more and more significant. In this paper, a secure RoF system based on key nested polar code and feedback neural network (FNN) is proposed. For the nested polar code, the original key is randomly selected from the constructed codebook and the index of key is encoded by inner polar code which is placed at the location with better channel quality bit of the frozen bit of outer polar code, for the other part of outer polar code, information bits are encrypted by chaotic sequence generated by 4-D cellular neural network. The polar coded sequence is mapped to the 16-QAM symbol for orthogonal frequency division multiplexing (OFDM) and then the OFDM signal is modulated to the optical pulse, which is delivered to users through 50 km standard single-mode fiber and 5 m wireless channel. In the receiver, successive cancellation list (SCL) decoder is used for decoding outer polar code and FNN is used for decoding inner polar code to reduce the latency. The experimental results show that, compared with the existing scheme, when the bit err rate is 10-3, the received optical power (ROP) gain of the proposed scheme with SCL2 decoder and SCL4 decoder is ∼1.2 dB and ∼1.6 dB, respectively. And compared with the traditional OFDM signal with polar code, when the bit err rate is 10-3, the ROP gain of the proposed scheme with SCL4 decoder is ∼1 dB. What's more, the randomness of the chaotic key sequence, the ability to resist brute-force attacks and the ability to resist chosen-plaintext attacks are elaborated. Therefore, the proposed scheme can greatly improve the security of the system while ensuring the correct transmission of information.

High-Quality and Low-Complexity Polar-Coded Radio-Wave Encrypted Modulation Utilizing Multipurpose Frozen Bits

In recent years, physical layer security (PLS), which utilizes the inherent randomness of wireless signals to perform encryption at the physical layer, has attracted attention. We propose chaos modulation as a PLS technique. In addition, a method for encryption using a special encoder of polar codes has been proposed (PLS-polar), in which PLS can be easily achieved by encrypting the frozen bits of a polar code. Previously, we proposed a chaos-modulated polar code transmission method that can achieve high-quality and improved-security transmission using frozen bit encryption in polar codes. However, in principle, chaos modulation requires maximum likelihood sequence estimation (MLSE) for demodulation, and a large number of candidates for MLSE causes characteristic degradation in the low signal-to-noise ratio region in chaos polar transmission. To address this problem, in this study, we propose a versatile frozen bit method for polar codes, in which the frozen bits are also used to reduce the number of MLSE candidates for chaos demodulation. The numerical results show that the proposed method shows a performance improvement by 1.7 dB at a block error rate of 10-3 with a code length of 512 and a code rate of 0.25 compared with that of conventional methods. We also show that the complexity of demodulation can be reduced to 1/16 of that of the conventional method without degrading computational security. Furthermore, we clarified the effective region of the proposed method when the code length and code rate were varied.

Joint Blind Reconstruction of the Cyclic Codes and Self-Synchronous Scramblers in a Noisy Environment

Reverse analysis of the intercepted signal to reconstruct the communication scheme used by the transmitter is a key problem in the non-cooperative context. In this paper, we propose a new algorithm for the joint blind reconstruction of the cyclic codes and self-synchronous scramblers directly using soft-decision sequences. First, we derive the conclusion that if the parity polynomial of the factor of the generator polynomial of the cyclic code and the feedback polynomial of the self-synchronous scrambler are multiplied, then the vector corresponding to the inverse polynomial of this product forms a parity-check relation with the row vector of the self-synchronously scrambled cyclic code bit matrix, which is constructed by the sequence of self-synchronously scrambled cyclic codes. To detect this parity-check relation, the concept of average parity-check probability (APCP) is defined, which uses the intercepted soft-decision sequence to measure the reliability of the parity-check relation. An optimal threshold based on the minimum error criterion is then derived. When the APCP is greater than this optimal threshold, the parity-check relation is considered to be detected, i.e., the corresponding irreducible polynomial is a factor of the generator polynomial of the cyclic code and the corresponding candidate feedback polynomial is the feedback polynomial of the self-synchronous scrambler. Therefore, the blind reconstruction problem in this paper is exactly equivalent to the hypothesis-testing problem. Simulation results show that the algorithm is more fault-tolerant than existing algorithms in noisy environments.

Multi-party simultaneous quantum identity authentication based on Greenberger-Horne-Zeilinger states

A successful implementation of any secure communication protocols requires the identity authentication as a prerequisite. Quantum identity authentication (QIA) can ensure the unconditional security of identity code. In this paper, we propose a multi-party simultaneous quantum identity authentication (MSQIA) protocol based on the Greenberger-Horne-Zeilinger (GHZ) state. In the protocol, N certified users can directly send their identity codes to the authenticator Alice simultaneously through quantum channels without classical communication, which enables Alice to authenticate their identity at the same time. Our protocol only requires Alice to perform the single-photon measurement. In theory, this protocol is unconditionally secure and one pair of (N + 1)-photon GHZ state can transmit N bits of identity codes. Our MSQIA protocol has application potential in the quantum communication field in the near future.

A Fragile Image Watermarking Scheme in DWT Domain Using Chaotic Sequences and Error-Correcting Codes.

With the rapid development of digital signal processing tools, image contents can be easily manipulated or maliciously tampered with. Fragile watermarking has been largely used for content authentication purposes. This article presents a new proposal for image fragile watermarking algorithms for tamper detection and image recovery. The watermarked bits are obtained from the parity bits of an error-correcting code whose message is formed from a binary chaotic sequence (generated from a secret key known to all legitimate users) and from bits of the original image. Part of the codeword (the chaotic bits) is perfectly known to these users during the extraction phase, adding security and robustness to the watermarking method. The watermarked bits are inserted at specific sub-bands of the discrete wavelet transform of the original image and are used as authentication bits for the tamper detection process. The imperceptibility, detection, and recovery of this algorithm are tested for various common attacks over digital images. The proposed algorithm is analyzed for both grayscale and colored images. Comparison results reveal that the proposed technique performs better than some existing methods.

Blind Identification of Polar Codes Based on Estimation and Derivation Approaches

The blind identification of polar codes is to identify code parameters such as the code length, the number and positions of information bits in a polar code in non-cooperative communications. In this letter, we propose two low-complexity algorithms to identify code length and information bits of polar codes, respectively, by taking the union of both the estimated code parameters and the derived code parameters from the allowable shortest code without the candidate code sets. Simulations show that our proposed scheme is robust to the error and significantly improves the identification performance as compared to the existing purely code parameter estimation approaches.

Non-Relaxation Deep Hashing Method for Fast Image Retrieval

Deep hashing methods utilize an end-to-end framework to mutually learn feature representations and hash codes, thereby achieving a better retrieval performance. Traditional supervised hashing methods adopt handcrafted features for hashing function learning and then generate hash codes through classification and quantization. The lack of adaptability and independence of the quantization procedure leads to low retrieval accuracy of supervised hashing methods with handcrafted features in image retrieval. In this study, a non-relaxation deep hashing method for fast image retrieval is proposed. In this method, a differentiable host thresholding function is used to encourage hash-like codes to approach -1 or 1 non-linearly at the output of the convolutional neural, instead of the symbol function for quantization used in the traditional method. The output of the host thresholding function is directly used to compute the network training error, and a loss function is elaborately designed with the norm to constrain each bit of the hash-like code to be as binary as possible. Finally, a symbol function is added outside the trained network model to generate binary hash codes for image storage and retrieval in a low-dimensional binary space. Extensive experiments on two large-scale public datasets show that our method can effectively learn image features, generate accurate binary hash codes, and outperform state-of-the-art methods in terms of the mean average precision.

Fast Successive-Cancellation Decoding of 5G Parity-Check Polar Codes

The successive-cancellation (SC) decoding of polar codes suffers from long latency due to its serial processing nature. The fast SC (FSC) decoding was proposed to address this issue by applying parallel decoders to various special nodes in the binary decoding tree. In this letter, we explore multiple special nodes containing parity-check bits of 5G polar codes. The characteristics of these nodes are well investigated. The corresponding fast decoders are developed, which significantly reduce the decoding latency without degrading the error-correction performance.

Design of a Low-Power and Low-Area 8-Bit Flash ADC Using a Double-Tail Comparator on 180 nm CMOS Process

This paper presents a low-area 8-bit flash ADC that consumes low power. The flash ADC includes four main blocks-an analog multiplexer (MUX), a comparator, an encoder, and an SPI (Serial Peripheral Interface) block. The MUX allows the selection between eight analog inputs. The comparator block contains a TIQ (Threshold Inverter Quantization) comparator, a control circuit, and a proposed architecture of a Double-Tail (DT) comparator. The advantage of using the DT comparator is to reduce the number of comparators by half, which helps reduce the design area. The SPI block can provide a simple way for the ADC to interface with microcontrollers. This mixed-signal circuitry is designed and simulated using 180 nm CMOS technology. The 8-bit flash ADC only employs 128 comparators. The applied input clock is 80 MHz, with the input voltage ranging from 0.6 V to 1.8 V. The comparator block outputs 127 bits of thermometer code and sends them to the encoder, which exports the seven least significant bits (LSB) of the binary code. The most significant bit (MSB) is decided by only one DT comparator. The design consumes 2.81 mW of power on average. The total area of the layout is 0.088 mm2. The figure of merit (FOM) is about 877 fJ/step. The research ends up with a fabricated chip with the design inserted into it.

Doped low-density parity-check codes

In this paper, we propose a doping approach to lower the error floor of Low-Density Parity-Check (LDPC) codes. The doping component is a short block code in which the information bits are selected from the coded bits of the dominant trapping sets of the LDPC code. Accordingly, an algorithm for selecting the information bits of the short code is proposed, and a specific two-stage decoding algorithm is presented. Simulation results demonstrate that the proposed doped LDPC code achieves up to 2.0 ​dB gain compared with the original LDPC code at a frame error rate of 10−6. Furthermore, the proposed design can lower the error floor of original LDPC codes.

Universal approach to sending-or-not-sending twin field quantum key distribution

We present a universal approach to sending-or-not-sending (SNS) protocol of twin-field quantum key distribution with the method of actively odd parity pairing. In this improved protocol, the code bits are not limited to heralded events in time windows participated by pulses of intensity μ z and vacuum. All kinds of heralded events can be used for code bits to distill the final keys. The number of intensities (3 or 4) and the kinds of heralded events for code bits are automatically chosen by the key rate optimization itself. Numerical simulation shows that the key rate rises drastically in typical settings, up to 80% improvement compared with the prior results. Also, larger intensity value can be used for decoy pulses. This makes the protocol more robust in practical experiments.

Non-Reconciled Physical-Layer Keys-Assisted Secure Communication Scheme Based on Channel Correlation.

Physical-layer key generation technology requires information reconciliation to correct channel estimation errors between two legitimate users. However, sending the reconciliation signals over the public channel increases the communication overhead and the risk of information leakage. Aiming at the problem, integrated secure communication schemes using non-reconciled keys have attracted extensive attention. These schemes exploit channel coding to correct both inconsistent keys and transmission error bits. Meanwhile, more redundant code bits must be added to correct errors, which results in a lower secure transmission rate. To address the problem, we analyze the merit of channel correlation between non-reconciled key generation and secure transmission. Inspired by this, we propose a non-reconciled physical-layer keys-assisted secure communication scheme based on channel correlation. First of all, the signal frame is designed to make use of channel correlation between non-reconciled key generation and secure transmission. Based on the channel correlation, non-reconciled keys are then generated from the wireless channel to encrypt transmitted data. Moreover, an adaptive coding algorithm based on the equivalent channel is presented to encode the data bits before encryption, to guarantee reliable transmission. Finally, theoretical analysis and simulations demonstrate the significant performance of the proposed scheme in terms of low bit error ratio and high secure transmission rate.

Joint Successive Cancellation List Decoding for the Double Polar Codes

As a new joint source-channel coding scheme, the double polar (D-Polar) codes have been proposed recently. In this letter, a novel joint source-channel decoder, namely the joint successive cancellation list (J-SCL) decoder, is proposed to improve the decoding performance of the D-Polar codes. We merge the trellis of the source polar code and that of the channel polar code to construct a compound trellis. In this compound trellis, the variable nodes corresponding to the information bits of the channel polar code and the variable nodes representing the high-entropy bits are merged into the joint source-channel (JSC) nodes. Based on the compound trellis, the J-SCL decoder is designed to recover the source messages by combining the source SCL decoding and channel SCL decoding. The proposed J-SCL decoder doubles the number of the decoding paths for each JSC node and low-entropy node, and then discard all but the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L$ </tex-math></inline-formula> paths with the smallest joint path-metric (JPM). For the JSC node, the JPM is updated considering both the channel decision log-likelihood ratios (LLRs) and the source decision LLRs. Simulation results show that the J-SCL decoder outperforms the turbo-like BP (TL-BP) decoder with lower complexity.

Optical likelihood calculation for quadrature phase‐shift keying signal based on silicon integrated waveguide

All-optical likelihood calculation has the potential to improve the performance of operating speed and power consumption in future communication systems. The author previously proposed a novel scheme of likelihood calculation, which is capable of applying multi-value modulation. However, these studies have a limitation that requires higher integration into an actual system. In this study, an optical device of likelihood calculation for a 4-bit quadrature phase-shift keying (QPSK) modulated signal (i.e. two sequential QPSK symbols) is demonstrated. The integrated device consists of two delayed interferometers with silicon waveguide. The device is designed according to the types of 4-bit code string as follows (00 00), (00 11), (11 00), and (11 11), and the output light waveform from the device is observed by an oscilloscope for a plurality of 4-bit QPSK signals. The light intensity obtained from the device accurately corresponds to the Hamming distance between the code string and the input signal. The results indicate that the proposed scheme correctly calculates a likelihood for a 4-bit QPSK signal at 10 Gbaud.

Robust image watermarking algorithm using chaotic sequences

This article presents a robust image watermarking scheme that provides high robustness and imperceptibility based on an innovative application of chaotic bits and error-correcting codes. The bits embedded in the image are the parity bits of an error-correcting code whose information sequence is formed by combining the watermark bits with chaotic bits generated from a secret key known to all legitimate users. Therefore, a part of the codeword is perfectly known to these users in the watermark extraction processing regardless of the strength of an attack. Thus, the error-correcting code capability is employed in recovering the watermark bits, improving the robustness of the method. The parity bits are embedded at specific frequencies of the discrete cosine transform and a parameter controls the compromise between robustness and imperceptibility. The proposed method is tested against several signal processing and geometric attacks, and comparison results reveal that it outperforms the existing schemes.

Enhancing Cross-Modal Hash Retrieval with Multiple Similarity Matrices

In order to further improve the performance of cross-modal retrieval, a cross-modal hash retrieval method integrating multi-level similarity information is proposed. First, self-attention method is used to enhance the text features, and a new fusion feature is constructed based on the original features and hash features of different modalities. Then, based on these three features, three auxiliary similarity matrices are constructed, and the fourth auxiliary similarity matrix is constructed by a weighted combination method. Finally, these four different matrices are used to calculate the loss functions between different similarity matrices and between different modalities. Since the four matrices include different feature forms and different matrix construction methods, they can better express similarity information of different modalities and improve the retrieval performance. The experiments are conducted on three benchmark datasets of Wikipedia, MIRFlickr and NUS-WIDE. The results show that the mAP values at different code bits of proposed method is better than that of many state-of-the-art methods, which verifies the effectiveness and robustness of our method.