Extra Bits Research Articles

Free Ride on LDPC Coded Transmission

In this paper, we formulate the problem to cope with the transmission of extra bits over an existing coded transmission link (referred to as coded payload link) without any cost of extra transmission energy or extra bandwidth. This is possible since a gap to the channel capacity typically exists for a practical code. A new concept, termed as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">accessible capacity</i> , is introduced to specify the maximum rate at which the superposition transmission of extra bits is reliable and has a negligible effect on the performance of the coded payload link. For a binary-input output-symmetric (BIOS) memoryless channel, the accessible capacity can be characterized as the difference between the channel capacity and the mutual information rate of the coded payload link, which can be numerically evaluated for very short payload codes. For a general payload code, we present a simple lower bound on the accessible capacity, given by the channel capacity minus the coding rate of the payload code. We then focus on the scenarios where low-density parity-check (LDPC) codes are implemented for the payload link. We propose to transmit extra bits by random superposition for encoding, and exhaustive search (with the aid of statistical learning) for decoding. We further propose, by establishing an auxiliary channel (called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">syndrome channel</i> ) induced from “zero-forcing” over the binary field, to transmit extra bits with structured codes such as repetition codes and first-order Reed-Muller (RM) codes. Numerical results show that up to 60 extra bits can be reliably transmitted along with a rate-1/2 LDPC code of length 8064.

Rate-Distortion Optimized Graph for Point Cloud Attribute Coding

Recent years have witnessed remarkable success of Graph Fourier Transform (GFT) in point cloud attribute compression. Existing researches mainly utilize geometry distance to define graph structure for coding attribute (e.g., color), which may distribute high weights to the edges connecting points across texture boundaries. In this case, these geometry-based graphs cannot model attribute differences between points adequately, thus limiting the compression efficiency of GFT. Hence, we firstly utilize attribute itself to refine the distance-based weight values by setting penalty function, which smoothens signal variations on graph and concentrates more energies in the low frequencies. Then, adjacency matrices acting as penalty function variables are transmitted to decoder with extra bit overheads. To balance the attribute smoothness on graph and the cost of coding adjacency matrices, we finally propose the graph based on Rate-Distortion (RD) optimization and find the optimal adjacency matrix. Experimental results show that our algorithm improves RD performance compared with competitive platforms. Moreover, additional experiments also analyze the gain source by evaluating the effectiveness of RD optimized graphs.

Edge-Aware Extended Star-Tetrix Transforms for CFA-Sampled Raw Camera Image Compression.

Codecs using spectral-spatial transforms efficiently compress raw camera images captured with a color filter array (CFA-sampled raw images) by changing their RGB color space into a decorrelated color space. This study describes two types of spectral-spatial transform, called extended Star-Tetrix transforms (XSTTs), and their edge-aware versions, called edge-aware XSTTs (EXSTTs), with no extra bits (side information) and little extra complexity. They are obtained by (i) extending the Star-Tetrix transform (STT), which is one of the latest spectral-spatial transforms, to a new version of our previously proposed wavelet-based spectral-spatial transform and a simpler version; (ii) considering that each 2D predict step of the wavelet transform is a combination of two 1D diagonal or horizontal-vertical transforms; (iii) weighting the transforms along the edge directions in the images. Compared with XSTTs, the EXSTTs can decorrelate CFA-sampled raw images well: they reduce the difference in energy between the two green components by about 3.38-30.08 % for high-quality camera images and 8.97-14.47 % for mobile phone images. The experiments on JPEG 2000-based lossless and lossy compression of CFA-sampled raw images show better performance than conventional methods. For high-quality camera images, the XSTTs/EXSTTs produce results equal to or better than the conventional methods: especially for images with many edges, the type-I EXSTT improves them by about 0.03-0.19 bpp in average lossless bitrate and the XSTTs improve them by about 0.16-0.96 dB in average Bjøntegaard delta peak signal-to-noise ratio. For mobile phone images, our previous work perform the best, whereas the XSTTs/EXSTTs show similar trends to the case of high-quality camera images.

Transmitting Extra Bits With Cyclically Shifted LDPC Codes

In this letter, we propose a simple yet efficient coding scheme to transmit extra bits by cyclically shifting a low-density parity-check (LDPC) coded sequence without any additional consumption in bandwidth or transmission energy. At the transmitter, the payload data is encoded into an LDPC coded sequence and then cyclically shifted under a pattern specified by the extra bits. At the decoder, the extra bits are first retrieved by estimating the number of cyclic shifts based on the hard or soft syndromes. After removing the effect of cyclic shift, the payload data is recovered by the LDPC decoder. Simulation results show that, with a 5G LDPC code of length 1910, up to 10 extra bits can be reliably transmitted with negligible influence on the reliability of the LDPC coded data.

Design, Implementation and Evaluation of a Low Redundant Error Correction Code

The continuous raise in the integration scale of CMOS technology has provoked an augment in the fault rate. Particularly, computer memory is affected by Single Cell Upsets (SCU) and Multiple Cell Upsets (MCU). A common method to tolerate errors in this element is the use of Error Correction Codes (ECC). The addition of an ECC introduces a series of overheads: silicon area, power consumption and delay overheads of encoding and decoding circuits, as well as several extra bits added to allow detecting and/or correcting errors. ECC can be designed with different parameters in mind: low redundancy, low delay, error coverage, etc. The idea of this paper is to study the effects produced when adding an ECC to a microprocessor with respect to overheads. Usually, ECC with different characteristics are continuously proposed. However, a great quantity of these proposals only present the ECC, not showing its behavior when using them in a microprocessor. In this work, we present the design of an ECC whose main characteristic is a low number of code bits (low redundancy). Then, we study the overhead this ECC introduces. Firstly, we show a study of silicon area, delay and power consumption of encoder and decoder circuits, and secondly, how the addition of this ECC affects to a RISC microprocessor.

Performance Enhancement of DWDM-FSO Optical Fiber Communication Systems Based on Hybrid Modulation Techniques under Atmospheric Turbulence Channel

In this paper, we enhance the performance efficiency of the free-space optical (FSO) communication link using the hybrid on-off keying (OOK) modulation, M-ary digital pulse position modulation (M-ary DPPM), and M-pulse amplitude and position modulation (M-PAPM). This work analyzes and enhances the bit error rate (BER) performance of the moment generating function, modified Chernoff bound, and Gaussian approximation techniques. In the existence of both an amplified spontaneous emission (ASE) noise, atmospheric turbulence (AT) channels, and interchannel crosstalk (ICC), we propose a system model of the passive optical network (PON) wavelength division multiplexing (WDM) technique for a dense WDM (DWDM) based on the hybrid fiber FSO (HFFSO) link. We use eight wavelength channels that have been transmitted at a data rate of 2.5 Gbps over a turbulent HFFSO-DWDM system and PON-FSO optical fiber start from 1550 nm channel spacing in the C-band of 100 GHz. The results demonstrate (2.5 Gbps × 8 channels) 20 Gbit/s-4000 m transmission with favorable performance. In this design, M-ary DPPM-M-PAPM modulation is used to provide extra information bits to increase performance. We also propose to incorporate adaptive optics to mitigate the AT effect and improve the modulation efficiency. We investigate the impact of the turbulence effect on the proposed system performance based on OOK-M-ary PAPM-DPPM modulation as a function of M-ary DPPM-PAPM and other atmospheric parameters. The proposed M-ary hybrid DPPM-M-PAPM solution increases the receiver sensitivity compared to OOK, improves the reliability and achieves a lower power penalty of 0.2–3.0 dB at low coding level (M) 2 in the WDM-FSO systems for the weak turbulence. The OOK/M-ary hybrid DPPM-M-PAPM provides an optical signal-to-noise ratio of about 4–8 dB of the DWDM-HFFSO link for the strong turbulence at a target BER of 10−12. The numerical results indicate that the proposed design can be enhanced with the hybrid OOK/M-DPPM and M-PAPM for DWDM-HFFSO systems. The calculation results show that PAPM-DPPM has increased about 10–11 dB at BER of 10−12 more than the OOK-NRZ approach. The simulation results show that the proposed hybrid optical modulation technique can be used in the DWDM-FSO hybrid links for optical-wireless and fiber-optic communication systems, significantly increasing their efficiency. Finally, the use of the hybrid OOK/M-ary DPPM-M-PAPM modulation schemes is a new technique to reduce the AT, ICC, ASE noise for the DWDM-FSO optical fiber communication systems.

Double generalized spatial modulation

AbstractIn this article, motivated by the enhanced spatial modulation and quadrature spatial modulation (QSM) systems, we proposed a new design of double generalized spatial modulation (DGSM), which further exploits the spatial domain not only for the transmission of more extra information bits by increasing the number of antenna index (AI) vectors in an AI vector set, but also for the achievable transmit diversity gain. In DGSM system, we first design the in‐phase and quadrature AI vector sets, whose each AI vector having one or more than one nonzero element equaling to “1” is used for the activation of one or more than one transmit antenna. Then, a spatial antenna index vector (SIV) is generated by adding an AI vector from the in‐phase AI set and another AI vector from the quadrature AI set. Furthermore, a data symbol (eg, QAM/PSK) is modulated on the SIV for forming multiple versions of the data symbol and then transmitted, the maximum likelihood (ML) and sphere decoder (SD) algorithm are applied for the DGSM system. Finally, the performance analysis, including in the spectral efficiency, the computational complexity comparison between the DGSM system with SD algorithm and the diversity‐achieving QSM (DA‐QSM) with ML detector, are provided. Also, the average bit error probability is analyzed. Simulation results using Monte Carlo are presented to show the improvement of bit error ratio performance in comparison with DA‐QSM and other spatial modulation schemes.

Constant-Length Labeling Schemes for Deterministic Radio Broadcast

Broadcast is one of the fundamental network communication primitives. One node of a network, called the s ource, has a message that has to be learned by all other nodes. We consider broadcast in radio networks, modeled as simple undirected connected graphs with a distinguished source. Nodes communicate in synchronous rounds. In each round, a node can either transmit a message to all its neighbours, or stay silent and listen. At the receiving end, a node v hears a message from a neighbour w in a given round if v listens in this round and if w is its only neighbour that transmits in this round. If more than one neighbour of a node v transmits in a given round, we say that a c ollision occurs at v . We do not assume collision detection: in case of a collision, node v does not hear anything (except the background noise that it also hears when no neighbour transmits). We are interested in the feasibility of deterministic broadcast in radio networks. If nodes of the network do not have any labels, deterministic broadcast is impossible even in the four-cycle. On the other hand, if all nodes have distinct labels, then broadcast can be carried out, e.g., in a round-robin fashion, and hence O (log n )-bit labels are sufficient for this task in n -node networks. In fact, O (log Δ)-bit labels, where Δ is the maximum degree, are enough to broadcast successfully. Hence, it is natural to ask if very short labels are sufficient for broadcast. Our main result is a positive answer to this question. We show that every radio network can be labeled using 2 bits in such a way that broadcast can be accomplished by some universal deterministic algorithm that does not know the network topology nor any bound on its size. Moreover, at the expense of an extra bit in the labels, we can get the following additional strong property of our algorithm: there exists a common round in which all nodes know that broadcast has been completed. Finally, we show that 3-bit labels are also sufficient to solve both versions of broadcast in the case where it is not known a priori which node is the source.

Discrete W Transform Based Index-Keying M-Ary DCSK for Non-Coherent Chaotic Communications

In this letter, a non-coherent discrete W transform based index-keying M-ary differential chaos shift keying (DWT-IK-MDCSK) system is proposed to tackle the high peak to average power ratio (PAPR) in the code-shifted DCSK systems and meet the demand of high-data-rate transmissions. In such system, multiple chaotic signals and their Hilbert transforms are cooperated closely to convey the M-ary information-bearing signals, and the resultant signals are extended by the index-keying discrete W vectors prior to being added up and transmitted over the channel. Since the index keying technique is used to select the specific discrete W vectors, extra information bits are conveyed by the indices of these vectors, thereby improving the data rate. Then, the analytical bit error rate (BER) expressions of DWT-IK-MDCSK are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels. Finally, simulation results show the DWT-IK-MDCSK system has a lower PAPR and better BER performance compared to its competitors.

Deep learning based HEVC in-loop filter and noise reduction

The lossy compression techniques at low bit rate often create ringing and contouring effects on the output images and introduce various blurring and distortion at block bounders. To overcome those compression artifacts different neural network based post-processing techniques have been experimented with over the last few years. The traditional loop-filter methods in the HEVC frame-work support two post-processing operations namely a de-blocking filter followed by a sample adaptive offset (SAO) filter. These operations usually introduce extra signaling bits and become overhead to the network with high-resolution video processing. In this study, we came up with a new deep learning-based algorithm for SAO filtering operations and substantiated the merits of the proposed method. We introduced a variable filter size sub-layered dense CNN (SDCNN) to improve the denoising operation and incorporated large stride deconvolution layers for further computation improvement. We demonstrate that our deconvolution model can effectively be trained by leveraging the high-frequency edge features learned in a shallow network using residual learning and data augmentation techniques. Extensive experiments show that our approach outperformed other state-of-the-art approaches in terms of SSIM, Bjøntegaard delta bit-rate (BD-BR), BD-PSNR measurements on the standard video test set and achieves an average of 8.73 % bit rate saving compared to HEVC baseline.

SLM Technique to Reduce PAPR and Improve BER in OFDM Systems

Through the combined use of multiple input, multiple output, and orthogonal frequency division multiplexing technologies, mankind has achieved a huge leap in the data rate of gigabit per second with the birth of 5G wireless technology. With frequency selective fading, multiple (OFDM MIMO) is possible. One of its most important performance concerns is PAPR (Peak-to-Average Power Ratio), which renders OFDM particularly vulnerable to harmonic distortion, reducing channel estimation accuracy and resulting in a lower bit error rate (BER). We propose a selective codeword shift mapping method for the MIMO-OFDM system (SCS-SLM). It lowers the PAPR and causes the power amplifier to operate in the non-linear area, resulting in intermodulation between sub-carriers, signal constellation, bit error rate distortion, as well as enhanced system performance. Furthermore, employing space-time-frequency block code (STFBC OFDM) orthogonal frequency division multiplexing might improve BER performance. This paper mentions a useful strategy for minimizing the PAPR, which is Selective Mapping. In addition, the bit error rate performance and, as a result, the process complexity for this system is discussed. In addition to the above-mentioned analysis, a thorough analysis of the mutual independence of the alternative OFDM signals generated using this technique is also discussed. Furthermore, this new approach has the important benefit of removing the extra bits on the side of the transmitted OFDM signal.

Design of ALU based on Majority Logic for Low Power Applications

Approximate calculations are a new nanotechnology paradigm for improving efficiency and reducing energy use. Most of the logic extends to many contemporary nanotechnological developments and is used for the design of digital circuits in its basic portion (3 input plurality, MV). This paper suggests implementations of additional compressors and ML multiplicators. An additional bit discovery circuit is used for the proposed compressors. The size of the multiplier is calculated by a control factor for the importance of different extra bits. The designs proposed are tested with hardware (for example, time frame and port complexity) as well as with error calculation. These designs have superior performance in terms of area and delay. The validity of the proposed designs is also shown by case tests of the error resistance implementation.

Novel OFDM transmission scheme using generalized prefix with subcarrier index modulation

The cyclic prefix (CP) is a prefix technique widely used in orthogonal frequency division multiplexing (OFDM) systems in order to eliminate the intersymbol interference (ISI) caused by the dispersion of wireless channels. However, CP reduces the number of symbols that can be transmitted in one OFDM symbol. Therefore, CP is one of the bottlenecks of OFDM systems limiting their spectral efficiency (SE). This limitation on the SE of the classical CP-based OFDM system is the main motivation for this work to introduce a novel method. In this paper, the design of a new CP structure, which is based on the generalized prefix (GP), is presented. In the proposed structure, extra bits are assigned to the GP structure to increase the SE of OFDM systems. Simulation results show that the proposed method has the same performance as conventional CP-based OFDM but higher spectral efficiency. Specifically, it is shown that the proposed method has 5.5% more spectral efficiency than the classical OFDM system. A simple algorithm is also proposed to detect the additional information bits conveyed by GP. As a result, the proposed method provides both high spectral efficiency and low computational complexity.

NC-OFDM-SPM: A Two-Dimensional Non-Coherent Modulation Scheme for Achieving the Coherent Performance of OFDM along with Sending an Additional Data-stream

A promising candidate solution for reducing complexity in future wireless systems is the use of non-coherent designs; however, it is very well known in the literature that non-coherent schemes perform worse than their coherent counterparts. To address this longstanding challenging trade-off, we demonstrate and prove in this work the ability of the proposed two-dimensional modulation scheme termed as non-coherent orthogonal frequency division multiplexing with subcarrier power modulation and differential phase shift keying in achieving the performance of a coherent design, while reducing complexity. Although the proposed design is non-coherent (i.e., it uses differential phase shift keying and power difference to convey information), it achieves the same bit error rate (BER) performance as conventional OFDM with coherent BPSK. Furthermore, since the proposed scheme employs two-dimensional modulations simultaneously (i.e., DPSK and subcarrier power levels), an additional data stream can be transmitted through the power subcarriers’ levels. Thus, the proposed design not only solves the trade-off between coherent and non-coherent modulations in terms of reliability by achieving the same BER, but also provides higher data rates by exploring the power domain as an additional dimension for conveying extra data bits, while maintaining low complexity transceiver design, thus making it very appealing for IoT applications.

Covert Channel-Based Transmitter Authentication in Controller Area Networks

In recent years, the security of automotive Cyber-Physical Systems (CPSs) is facing urgent threats due to the widespread use of legacy in-vehicle communication systems. As a representative legacy bus system, the Controller Area Network (CAN) hosts Electronic Control Units (ECUs) that are crucial for the vehicles functioning. In this scenario, malicious actors can exploit the CAN vulnerabilities, such as the lack of built-in authentication and encryption schemes, to launch CAN bus attacks (e.g., suspension, injection, and masquerade attacks) with life-threatening consequences (e.g., disabling brakes). In this article, we present TACAN (Transmitter Authentication in CAN), which provides secure authentication of ECUs on the legacy CAN bus by exploiting the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">covert channels</i> , without introducing CAN protocol modifications or traffic overheads (no extra bits or CAN messages are used). TACAN turns upside-down the originally malicious concept of covert channels and exploits it to build an effective defensive technique that facilitates transmitter authentication via a centralized, trusted Monitor Node. TACAN consists of three different covert channels for ECU authentication: 1) the Inter-Arrival Time (IAT)-based, leveraging the IATs of CAN messages; 2) the Least Significant Bit (LSB)-based, concealing authentication messages into the LSBs of normal CAN data; and 3) a hybrid covert channel, exploiting the combination of the first two. In order to validate TACAN, we implement the covert channels on the University of Washington (UW) EcoCAR (Chevrolet Camaro 2016) testbed. We further evaluate the bit error, throughput, and detection performance of TACAN through extensive experiments using the EcoCAR testbed and a publicly available dataset collected from Toyota Camry 2010. We demonstrate the feasibility of TACAN and the effectiveness of detecting CAN bus attacks, highlighting no traffic overheads and attesting the regular functionality of ECUs.

Polarized modulation and receivers for wireless communication

Achieving increase in spectral efficiency has always been a major aspect in communication systems. Our work emphasises the application of dual polarized modulation in a wireless environment. Our main goal is to increase the throughput of the system. We aim to increase the spectral efficiency and throughput without an increment of radiated energy without any Channel State Information at Transmitter (CSIT) and feedback at the transmitter The proposed dual Polarized Modulation (DPMOD) scheme exploits the polarization diversity reducing the required SNR (Eb/N0) and adding an extra bit and achieves the same Bit Error Rate (BER) carrying extra information.

Orthogonal frequency division multiplexing with index modulation by using multiple constellation sets

AbstractIn this article, a new transmission method named enhanced orthogonal frequency division multiplexing (E‐OFDM) is proposed to increase the spectral efficiency (SE) of the OFDM. The proposed method conveys information bits not only by the M‐ary symbols but also by the multiple different constellation sets. In the proposed method, we build the sub‐blocks by splitting the whole OFDM into pieces. Then, we use different constellation sets in each sub‐block and we assign the extra bits to them to increase the SE of the OFDM systems. Consequently, at the same modulation level, the proposed method has higher SE than the conventional OFDM system. The simulation results also show that the proposed method achieves better bit error rate (BER) performance than the conventional OFDM system with tolerable complexity. For example, the proposed method with a sub‐block size 2 doubles the SE of the conventional OFDM method with BPSK modulation, and also it has approximately 1.6 dB better BER performance than the conventional OFDM at BER =10−4. New constellation designs and receiver algorithm for the detection of additional bits are also presented.

A K-Band Variable-Gain Phase Shifter Based on Gilbert-Cell Vector Synthesizer With RC–RL Poly-Phase Filter

A K-band variable-gain phase shifter using a Gilbert-cell vector synthesizer with a current digital-to-analog converter (DAC) and an RC-RL poly-phase filter (PPF) is presented, which is fabricated with a 65-nm RF CMOS process. It controls both gain and phase with low phase and gain variations as well as a low insertion loss. The Gilbert cell synthesizes a vector by summing in-phase (I) and quadrature (Q) phase signals of which the amplitudes are decided by the tail currents of the summing cells, respectively. The tail currents are given by current DACs, which are particularly designed to make the synthesizer have a constant output impedance in all phase and gain states. Because the gain and phase control resolutions depend on those of the current DACs, the size and insertion loss of the variable-gain phase shifter are not dependent on the control resolutions. The total root-mean-square (rms) phase and gain errors are measured to be 0.488° and 0.098 dB for 4096 states of the 7-bit 360° phase and 5-bit 17.8-dB gain controls, respectively, which are calibrated with extra 2-phase and 1-gain control bits. It shows -3.5 dB maximum gain including ON-chip balun losses with 6.6-mW dc power consumption.

Fully Generalized Spatial Modulation utilizing Transmit Antenna Grouping

One of the recently modified multiple-input multiple-output (MIMO) systems is the spatial modulation (SM). Although SM is considered as MIMO in its composition, a single antenna at the transmitting side is activated at any time instant. Among all transmitting antenna, the selection of this active antenna isn't random but rather chosen based on extra bits, called spatial bits, transmitted besides the conventional digitally modulated bits. In addition to the transmission of additional bits, SM wireless communication system achieves an enhanced power efficiency, low error rate, low complexity at receiver, and completely inter-channel interference (ICI) elimination. On the other side, SM suffers from the dramatic increase in the number of required transmit antennas to achieve a small improvement in data rate and low spectral efficiency when compared with multiplexing MIMO (Mux-MIMO). The exponential increase in the data rate of the SM scheme became linear thanks to the fully generalized spatial modulation scheme (F-Gen-SM). Although the F-Gen-SM scheme overcame one of the SM disadvantages, the achievable data rate still low when compared with Mux-MIMO. Grouping generalized spatial modulation scheme (Gr-Gen-SM) tries to find a compromise between the advantage of SM and the high spectral efficiency of Mux-MIMO. Gr-Gen-SM achieves high spectral efficiency but loses most of the SM advantages. This paper introduces a new F-Gen-SM scheme utilizing the idea of dividing transmit antennas into groups (F-Gr-Gen-SM). This proposed scheme provides an improvement on data rate while preserving the advantages of SM as much as possible.

Virtual Spatial Channel Number and Index Modulation

This paper proposes a novel precoding‐aided and efficient data transmission scheme called virtual spatial channel number and index modulation (VS‐CNIM), which conveys extra data by changing both the number and index of active virtual parallel channels of multiple‐input multiple‐output (MIMO) channels, obtained through the singular value decomposition (SVD) in each time slot. Unlike the conventional virtual spatial modulation (VSM), where extra data bits are transmitted only using index of active virtual parallel channels, the VS‐CNIM scheme, depending on incoming information bits, transmits extra bits utilizing both the number and indices of active parallel channels along the bits carried by M‐ary constellation symbols. Therefore, VS‐CNIM provides significantly superior spectral efficiency (SE) compared to VSM. Considering the influence of imperfect channel estimation, a closed‐form upper bound is derived on average bit error probability (ABEP). The asymptotic performance is also analyzed, which gives the coding gain and diversity order and describes error floor under the consideration of perfect and imperfect channel estimation, respectively. Monte Carlo simulations exhibit that the VS‐CNIM scheme achieves considerably better error performance and high SE than precoding‐aided SM (PSM) and VSM schemes.