Additional Bits Research Articles

Optical dual-mode index modulation aided OFDM for visible light communications

Dual-mode index modulation aided orthogonal frequency multiplexing (DM-OFDM) is recently proposed, where the spectral efficiency is enhanced compared with conventional OFDM schemes. In this paper, we propose two different optical DM-OFDM schemes for visible light communications, dual-mode index modulation aided DC-biased optical OFDM (DM-DCO-OFDM) and dual-mode index modulation aided unipolar OFDM (DM-U-OFDM). In the optical DM-OFDM schemes, subcarriers are partitioned into OFDM subblocks, divided into two groups within each subblock, and modulated by two different modes of constellations. Additional information bits can be transmitted implicitly by the indices of subcarriers modulated by the same constellation alphabet. In order to generate non-negative signals, the real-valued time-domain signals are DC-biased in DM-DCO-OFDM, whilst positive and negative signals are transmitted separately in DM-U-OFDM. At the receiver, both a maximum-likelihood (ML) detector and a log-likelihood ratio (LLR) detector are employed for signal demodulation. Besides, simulation results demonstrate that the proposed optical DM-OFDM schemes are capable of enhancing the spectral efficiency compared with other existing optical OFDM schemes, and DM-DCO-OFDM as well as DM-U-OFDM can achieve significant performance gains over their conventional counterparts at the same spectral efficiency, when the nonlinear transfer characteristic of light-emitting diodes (LEDs) is considered.

Robust distributed video coding for wireless multimedia sensor networks

Coding complexity and error-resilience are the two key factors for video streaming in Wireless Multimedia Sensor Networks (WMSNs). Towards this objective, this paper proposes a Robust Distributed Video Coding (RDVC) framework to optimize the quality of video transmission for WMSNs. A new error-resilient Key frame coding scheme is proposed based on the protection of Wyner-Ziv Coding (WZC), in which additional Wyner-Ziv bits play a significant role for better error resilience and better Rate/Distortion (RD) performance. In addition, following the theoretical background of Distributed Joint Source Channel Coding (DJSCC), a novel distributed source channel codec based on Group Puncture Rate Adaptive IRA code (GPRA-IRA) is proposed, upon which the error-resilient Wyner-Ziv codec is designed. These experimental results show that the proposed RDVC scheme outperforms the relevant coding in terms of RD performance, notably by up to 1-3 dB, while achieving a lower encoding complexity.

Novel Error Detection Algorithm for LZSS Compressed Data

Conventional error detection schemes, such as the repetition code, parity bit, and Hamming code, have been used to detect bit errors in data. These conventional schemes require the insertion of additional bits to detect bit errors, but the code rate decreases in proportion to the number of additional bits. In order to avoid this problem, in this paper, we introduce three special bit patterns in Lempel-Ziv–Storer-Szymanski (LZSS) compressed data. In addition, based on the three bit patterns, we propose a novel error detection algorithm for LZSS compressed data, which does not need to use additional bits to detect bit errors. In the simulation, it is demonstrated that the compression ratio and running time of the proposed algorithm are better than those of the conventional schemes, such as repetition code, parity bit, and Hamming code. In addition, it is shown that when more than/equal to seven bit errors occur, the proposed algorithm nearly always detects the presence of errors in the LZSS compressed data.

Code-Shifted Differential Chaos Shift Keying with Code Index Modulation for High Data Rate Transmission

In the general code-shifted differential chaos shift keying (GCS-DCSK) system, multiple bit-streams are simultaneously carried by CS-DCSK signal using Walsh codes. However, its data rate is limited by the available Walsh codes in the Walsh code matrix due to orthogonality constraint of GCS-DCSK signal. In this paper, we propose a new GCS-DCSK scheme with code index modulation (CIM-CS-DCSK), which can achieve higher spectrum efficiency using code index modulation to carry additional bits. In the proposed scheme, the reference chaotic signal is the same as that of GCS-DCSK, and the multiple information bearing signals are simultaneously modulated by the information symbols and the selected Walsh codes with specific indices, which are determined by an integer sequence mapped from information symbols via the natural numbers to $k$ -combinations mapping method. We derive bit error rate of the proposed scheme over the additive white Gaussian noise channel. The numerical results not only verify our analysis but also show the advantage of the proposed scheme over GCS-DCSK. Through analyzing and comparing the numbers of carried bits per transmitted symbol of CIM-CS-DCSK and GCS-DCSK, it is shown that the proposed scheme can obtain higher data rate than GCS-DCSK with the same resource constraints.

Redundancy Allocation Based on the Weighted Mismatch-Rate Slope for Multiple Description Video Coding

Multiple description coding (MDC) is a robust coding technique for video transmission over error prone networks, whereby the video is encoded into multiple descriptions with some redundancy between the descriptions. This redundancy leads to error resiliency in the case of packet loss during the network transport. However, the amount of this redundancy has a critical role in MDC performance. Therefore, a crucial problem in MDC is to find what the optimum amount of redundancy budget is, and then how this redundancy budget can be optimally allocated to the frames. To solve this problem, we propose a scheme in which the redundancy budget is allocated to the frames based on the weighted mismatch-rate slopes so that this additional bitrate can attain maximum distortion reduction. The redundancy is added gradually so that fine tuning of the utilized bitrate is achievable. We have verified our proposed scheme by implementing it in H.264/AVC reference software JM16.0, and running experiments against two representative reference methods. Our experiments show that our scheme not only minimizes the end-to-end distortion with a rate-distortion performance that is better than the reference methods, especially for high PLRs, but also entirely uses the available bandwidth, unlike the reference methods.

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Vector OFDM With Index Modulation

The concept of index modulation (IM) has gained increased attention in recent years. As a member of the IM family, orthogonal frequency division multiplexing with index modulation (OFDM-IM), which is able to convey additional information bits using the indices of the active subcarriers, has emerged as an attractive physical layer transmission technique. Vector OFDM (V-OFDM) has inherently good peak-to-average-power ratio (PAPR) feature and good bit error rate (BER) performance due to the nearly full diversity gains achieved by most of its sub-blocks. In this paper, in order to improve the BER performance of OFDM-IM and reduce the PAPR of the transmit signal, we propose an enhanced OFDM-IM scheme termed vector OFDM with index modulation (V-OFDM-IM). In addition to the structure of the transceiver, a complexity reduced maximum likelihood detector is presented. To further reduce the detection complexity, a near-optimal detector based on sequential Monte Carlo technique is introduced. The average bit error probability of the proposed scheme is derived in closed form over frequency-selective block Rayleigh-fading channel. Both the theoretical and the simulation-based results show that, under the same spectrum efficiency, V-OFDM-IM outperforms the conventional OFDM-IM and OFDM.

Generalized Frequency Division Multiplexing With Flexible Index Modulation

After the vision and the overall objectives of future wireless networks for 2020 and beyond have been defined, standardization activities for fifth generation (5G) wireless networks have been started. Although it is expected that 5G new radio (NR) will be based on cyclicly prefixed orthogonal frequency division multiplexing (CP-OFDM)-based waveforms along with multiple waveform numerologies, the sufficiency of CP-OFDM-based NR is quite disputable due to the continuing massive growth trend in number of wireless devices and applications. Therefore, studies on novel radio access technologies (RATs) including advanced waveforms and more flexible radio accessing schemes must continue for future wireless networks. Generalized frequency division multiplexing (GFDM) is one of the prominent non-CP-OFDM-based waveforms. It has recently attracted significant attention in research because of its beneficial properties to fulfill the requirements of future wireless networks. Multiple-input multiple-output (MIMO)-friendliness is a key ability for a physical layer scheme to satisfactorily match the foreseen requirements of future wireless networks. On the other hand, the index modulation (IM) concept, which relies on conveying additional information bits through indices of certain transmit entities, is an emerging technique to provide better spectral and energy efficiency. In this paper, considering the advantages of non-CP-OFDM-based waveforms and the IM concept, we present a framework, which integrates GFDM with space and frequency IM schemes to provide flexible and advanced novel RATs for future wireless networks. Several MIMO-GFDM schemes are provided through the proposed framework and their bit error ratio performances, computational complexities, and spectral efficiencies are analyzed. Based on the obtained results, a guideline for selecting the proper MIMO-GFDM scheme considering target performance criterion is given. It has been demonstrated that the proposed framework has a strong potential to engineer the space-frequency structure according to channel conditions and use cases, and it provides a great flexibility that can be easily tuned to address the required performance criterion.

Practical Implementation of Index Modulation-Based Waveforms

Orthogonal frequency division multiplexing (OFDM) with index modulation (OFDM-IM) technique has been recently proposed to provide performance improvements over conventional OFDM. OFDM-IM includes a different data transmission mechanism, where additional data bits are transmitted over subcarrier patterns by specifically activating selected subcarriers and nulling the others. However, such a mechanism inherently causes some inefficiency due to the inactive subcarriers. To improve the spectral efficiency of the OFDM-IM technique, dual-mode OFDM with index modulation (DM-OFDM) is proposed, where nulled subcarriers are activated by using a second signal constellation. With DM-OFDM, a significant data rate improvement can be obtained. As an important missing issue in the literature, OFDM-IM and its effective variations, such as DM-OFDM, have only been studied in terms of computer simulations and theoretical analysis. Therefore, their real-time performance is not yet investigated to assess their potential for next-generation networks. Addressing this gap, in this paper, OFDM-IM and DM-OFDM techniques are implemented in real-time by using software defined radio technology. National Instruments USRP-2921 nodes are used in a single-input single-output configuration. With this implementation, detailed real-time results and performance observations are provided. Moreover, a hybrid OFDM-IM (H-OFDM-IM) scheme, which can be seen as the combination of OFDM-IM and DM-OFDM, is proposed by targeting the limitations of both OFDM-IM and DM-OFDM in terms of spectral containment and error performance. With H-OFDM-IM, noticeable improvements in spectral containment and error performance can be obtained, and these observations show its suitability for real-time use and next-generation networks. With comprehensive computer simulation and test results, these claims are verified.

Error Probability Analysis of OFDM-IM With Carrier Frequency Offset

OFDM-IM, which uses the indices of active subcarriers to carry additional information bits, is a novel multi-carrier transmission technique. In this letter, by exploiting the special design of OFDM-IM, we propose an analytical approach to evaluate the error probability of OFDM-IM subject to carrier frequency offset (CFO) in fading channels, where the inter-carrier interference (ICI) is properly divided into two parts: the intra-subblock ICI and the inter-subblocks ICI. Simulation results illustrate that the results of theoretical analysis are quite accurate, and OFDM-IM outperforms the conventional OFDM when CFO exists.

Equiprobable Subcarrier Activation Method for OFDM With Index Modulation

Orthogonal frequency division multiplexing with index modulation (OFDM-IM) conveys additional information bits via the indices of active subcarriers. Consequently, the determination of the active subcarriers according to the incoming bits arises as a challenging problem. The existing solution resorts to the lexicographic ordering, which leads to a low implementation complexity but an unequal subcarrier activation probability. This letter proposes a distinct solution that allows the equiprobable activation of all OFDM-IM subcarriers with comparable implementation complexity. The signal-to-noise ratio gain achieved by the proposed solution is also analyzed. Computer simulations reveal the advantages of the proposed solution.

LZ78 압축 데이터의 구조적 패턴에 기반한 새로운 오류 검출 알고리즘

본 논문에서는 LZ78 알고리즘으로 압축된 데이터의 오류 검출 알고리즘을 제안하였다. 기존의 비트 오류를 검출하는 방법들은 송신 단에서 패리티(parity) 비트를 추가하여 전송한 후, 수신 단에서 값이 '1'인 비트의 개수를 이용하여 오류를 검출하는 방법을 사용하였다. 이러한 기존의 방법들은 오류 검출을 위하여 추가적인 비트를 사용하는데 이는 데이터의 크기를 줄이는 것을 목적으로 하는 압축 데이터에 대해서는 적합하지 않은 방법이다. 따라서 본 논문에서는 LZ78 알고리즘 기반의 압축 데이터에서 추가적인 비트를 사용하지 않고 알고리즘의 구조적인 특성을 이용하여 오류를 검출하는 방법을 제안하였다. 실험을 통하여 제안하는 알고리즘의 오류 검출율에 대한 효율이 기존의 오류 검출 알고리즘에 비해 약 1.3 배 높은 효율을 가지는 것을 보였다. In this paper, we propose a novel error detection algorithm for LZ78-compressed data. The conventional error detection method adds a certain number of parity bits in transmission, and the receiver checks the number of bits representing '1' to detect the errors. These conventional methods use additional bits resulting in increased redundancy in the compressed data which results in reduced effectiveness of the final compressed data. In this paper, we propose error detection algorithm using the structural properties of LZ78 compression without using additional bits in the compressed data. The simulation results show that the error detection ratio of the proposed algorithm is about 1.3 times better for error detection than conventional algorithms.

Quantum computing: Efficient fault tolerance.

Dealing with errors in a quantum computer typically requires complex programming and many additional quantum bits. A technique for controlling errors has been proposed that alleviates both of these problems.

Storage-Free Memory Dependency Prediction

Memory Dependency Prediction (MDP) is paramount to good out-of-order performance, but decidedly not trivial as a all instances of a given static load may not necessarily depend on all instances of a given static store. As a result, for a given load, MDP should predict the exact store instruction the load depends on, and not only whether it depends on an inflight store or not, i.e., ideally, prediction should not be binary. However, we first argue that given the high degree of sophistication of modern branch predictors, the fact that a given dynamic load depends on an inflight store can be captured using the binary prediction capabilities of the branch predictor, providing coarse MDP at zero storage overhead. Second, by leveraging hysteresis counters, we show that the precise producer store can in fact be identified. This embodiment of MDP yields performance levels that are on par with state-of-the-art, and requires less than 70 additional bits of storage over a baseline without MDP at all.

Reversible Data Hiding in Encrypted Images Based on Progressive Recovery

This paper proposes a method of reversible data hiding in encrypted images (RDH-EI) based on progressive recovery. Three parties are involved in the framework, including the content owner, the data-hider, and the recipient. The content owner encrypts the original image using a stream cipher algorithm and uploads a ciphertext to the server. The data-hider on the server divides the encrypted image into three channels and, respectively, embeds different amount of additional bits into each one to generate a marked encrypted image. On the recipient side, additional message can be extracted from the marked encrypted image, and the original image can be recovered without any errors. While most of the traditional methods use one criterion to recover the whole image, we propose to do the recovery by a progressive mechanism. Rate-distortion of the proposed method outperforms state-of-the-art RDH-EI methods.

Data hiding in AMBTC images using quantization level modification and perturbation technique

A novel data hiding method for Absolute Moment Block Truncation Coding (AMBTC) compressed image based on quantization level modification is proposed. Blocks of AMBTC-compressed image are classified into two categories, namely smooth and complex, according to a predefined threshold. For smooth blocks, the bitmap is replaced by secret data for data embedment. Meanwhile, the corresponding quantization levels are modified to achieve a minimum distortion. If a larger payload is required, the modified quantization levels can be further perturbed for carrying two additional bits. If the blocks are complex, one data bit can be embedded with no distortion by swapping the values of the two quantization levels together with bitmap flipping. In addition, a suppress threshold mechanism is used to prevent from the application of the perturbation technique at low payload to maintain the image quality. The proposed method minimizes the distortion of each stego block while ensuring high payload, thus the embedding efficiency can be enhanced. Experimental results demonstrate the improvement of the proposed method compared with other related state-of-art works.

Reversible data hiding for encrypted signals by homomorphic encryption and signal energy transfer

Reversible data hiding for encrypted signals with prefect reconstruction of directly decrypted signals is introduced in this paper. Each unit in the original image is separated into three components by energy transfer equation, and each component is encrypted by Paillier homomorphic encryption. Additional bits are concealed into the encrypted image by manipulating the encrypted signals. Finally, the original image can be perfectly recovered when direct decryption is applied. The embedded bits are lossless extracted as well. Optimal visual quality and improved embedding rate are obtained by the proposed approach, since the value of the directly decrypted unit is the same as the original one. Experimental results and comparisons are demonstrated to illustrate the effectiveness and advantages of the proposed method. Moreover, the proposed method can be extended to deal with encoded multimedia, which further enriches the application scenarios.

Reliable data transfer Rendezvous protocol in wireless sensor networks using 2D-SEC-DED encoding technique

Many applications in Wireless Sensor Networks (WSNs) require all data to be transmitted with minimal or without loss, what implies that reliability is an important characteristic. In any WSN, there are two basic approaches to recover erroneous packets. One way is to use Automatic Repeat reQuest (ARQ), and another is Forward Error Correction (FEC). The error-control systems for applications based on ARQ use error detection coupled with retransmission requests to maximize reliability at some cost to throughput. Error detection is generally provided by the lower protocol layers which use checksums (e.g. Cyclic Redundancy Checksums (CRCs)) to discard corrupted packets and trigger retransmission requests. In these solutions event a single erroneous bit can render a packet useless to the end user. Having in mind that in WSNs the power is scarce and is primarily consumed by wireless transmission and reception, we propose to use FEC rather than ARQ. FEC is a way of correcting packets by transmitting additional information bits with aim to reduce the frequency of retransmission requests. During this, data bytes are optionally encoded after being fragmented with Error Correcting Code (ECC) to recover data bits in case of small number of bit errors. Various FEC encoding schemes such as erasure and Hamming based codes are available. The choice of the encoding schemes depends on the applications and error characteristics (error models/patterns) of the wireless channel. Erasure encoding is preferable for usage when the error pattern is burst dominated, while Hamming encoding when noise causes random errors. Our observations show that most bit errors are single-bit or double-bit errors and burst errors are present but rare. In this work, an efficient Hamming based FEC encoding scheme of relatively low complexity called Two Dimensional-Single Error Correcting-Double Error Detecting (2D-SEC-DED), intended to minimize packet retransmissions and to save energy, has been developed. Such FEC scheme can be used to correct all single-bit and 99.99%of double/multiple-bit errors. Since the radio block is dominant energy consumer within a Sensor Node (SN), we focus our attention to answer the question: which is the adequate metric to use, and under what conditions to accurately characterize the quality of the communication, related to reliable data transfer, with minimal energy consumption. To this end, as first, in a case when the bit error is not high and most errors are single-bit, we show that 2D SEC-DED encoding scheme is more energy efficient in comparison to erasure encoding. As second, the advantages of using 2D-SEC-DED in respect to CRC (NO-FEC) encoding, concerning decreasing the energy consumption and increasing the reliability of the radio block are derived through implementation of two versions of the Rendezvous Protocol for Long Living (RPLL) referred as Modified-RPLL (M-RPLL as FEC based) and Ordinary-RPLL (O-RPLL as NO-FEC), respectively.

Probabilistic Directed Writebacks for Exclusive Caches

Energy is an increasingly important consideration in memory system design. Caches improve energy efficiency by decreasing execution time and reducing the number of main memory accesses, but they suffer from known inefficiencies: the last-level cache (LLC) tends to have a high miss ratio while simultaneously storing many blocks that are never referenced. Because these blocks are not referenced before eviction, we can write them directly to memory rather than to the LLC. To do so, we must predict which blocks will not be referenced. Previous approaches rely on additional state at the LLC and/or extra communication. We show that by predicting working set size per program counter (PC), we can decide which blocks have low probability of being referenced. Our approach relies on the insight that it is possible to makes this prediction based solely on the address stream as seen by the level-one data cache (L1D), eliminating the need to store or communicate PC values between levels of the cache hierarchy. We require no modifications to the LLC. Our approach uses Flajolet andMartin's probabilistic counting to keep the state small: two additional bits per L1D block, with an additional 6KB prediction table. This approach yields a large reduction in number of LLC writebacks: 25% fewer for SPEC on average, 80% fewer for graph500, and 67% fewer for an in-memory hash table.

Design of Novel MSK Architectures using R-F Bit

In this paper, we present two novel reformulations (1) and (20) for MSK (Minimum Shift Keying) modulation technique. By using these novel reformulations, we find an additional switching bit, referred to as R-F bit, and propose a novel MSK architecture. Compared to known prior MSK architectures, our architecture offers significant advantages with respect to power consumption and hardware efficiency. Additionally, a pre-computation technique is used to reduce ram bit utilization (RBU) of the proposed modulator. Considering the whole modulation procedure, this approach reduces the RBU of the proposed architecture by 75%. The experimental results show that our architecture is very suitable for MSK modulation. DOI: http://dx.doi.org/10.5755/j01.eie.22.3.15322