Channel coding for digital HDTV terrestrial broadcasting

In order to transmit the HDTV signal in 6 MHz, the four United States digital HDTV proponents, the DigiCipher, DSC-HDTV, ADTV and ATVA-P systems, are reducing the video data rate of HDTV to 15-17 Mb/s, a compression ratio of approximately 60-70 times. The high compression dictates that channel coding be used to avoid block errors and multiframe error propagation. High efficiency in channel utilization required by the 6-MHz limitation means that the channel must be properly equalized and that the multipath and interfering signals must be severely limited. The channel coding techniques used for error reduction include data interleaving, error detection and replacement, and error correction at different levels of protection for bits and blocks of unequal importance     

Channel Error Recovery for Transform Image Coding

A method is presented to automatically inspect the block boundaries of a reconstructed two-dimensional transform coded image, to locate blocks which are most likely to contain errors, to approximate the size and type of error in the block, and to eliminate this estimated error from the picture. This method uses redundancy in the source data to provide channel error correction. No additional channel error protection bits or changes to the transmitter are required. It can be used when channel errors are unexpected prior to reception.     

8-QAM Software Defined Radio Based Approach for Channel Encoding and Decoding Using Forward Error Correction

The aim of this paper is to use a software defined radio (SDR) based approach in order to select channel encoding and decoding method accordingly using 8-QAM (Quadrature Amplitude Modulation) in terms of bit error rate (BER). By selecting a higher order format of QAM, we are able to carry more bits of information per symbol; also the data rate can be increased thus achieving greater distance between adjacent points in the I–Q plane by distributing the points more evenly. Hence the constellation points are more distinct and data errors are reduced. In the present work 8-QAM is chosen as modulation scheme so that balance can be maintained between higher data rates while maintaining an acceptable bit error rate for SDR. Channel coding schemes forward error correction are used where the re-transmission of the data is not feasible, thus redundant bits are added along with the message bits and transmitted through the channel. On the receiver side, this channel coded signal is decoded in order to get back the original data even if the channel coded signal undergoes some interference from the noise in the transmission medium. The performance is then analyzed in terms of BER for Hamming and convolution coding algorithms at a particular value of SNR in LabVIEW graphical programming. With the help of LabVIEW we were able to design the systems in a block-based manner in shorter time as compared to the commonly used text-based programming languages.     

Near-optimal, single-synchronization-error-correcting code

A synchronization error is said to occur when either a bit which does not belong is detected in a channel between bits which were transmitted, or a bit which was transmitted is never detected at the output. A block code which corrects a single synchronization error per block is presented, and it is shown that this code has, at most, three bits more redundancy than that of an optimal code for this class of errors. The code has the beneficial property that it is possible to separate the information positions from the check positions, and an appropriate method of encoding is shown.     

A novel selected mapping technique for PAPR reduction in OFDM systems

Selected mapping (SLM) is a well-known method for reducing the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems. The main drawback of this technique is that, for each data block, it requires the transmission of several side information bits, which results in some data rate loss. These redundant bits are so critical to the error performance of the system that they need in practice to be protected by a powerful channel code. This increases the system complexity and transmission delay, and decreases the data rate even further. In this paper, we propose a novel SLM method for which no side information needs to be sent. By considering the example of an OFDM system using 16-QAM modulation, it is shown that the proposed method performs very well both in terms of PAPR reduction and bit error rate at the receiver output.     

The coding of image sequences by wavelets, wavelet packets andother subband coding schemes

For the terrestrial broadcasting of high-definition television (HDTV) in North America the discrete cosine transform (DCT), Huffman (lossless) coding and motion detection, estimation and compensation have been used to compress raw HDTV rates of 1.0-1.2 Gbps. Compressed and compacted video bit rates range from 12.59 Mbps to 13.60 Mbps for 16-QAM transmission and from 17.47 to 18.88 for 32-QAM transmission. MPEG source coding schemes, are used in a proposed HDTV system and in the Grand Alliance proposal. They share features in common with other source coding schemes which have been employed. It seems likely that compression and compaction to an HDTV video bit rate below 10 Mbps should be attainable. The methods discussed in this paper provide hope for realizing this goal     

Carrier synchronization for 3- and 4-bit-per-symbol optical transmission

We investigate carrier synchronization for coherent detection of optical signals encoding 3 and 4 bits/symbol. We consider the effects of laser phase noise and of additive white Gaussian noise (AWGN), which can arise from local oscillator (LO) shot noise or LO-spontaneous beat noise. We identify 8- and 16-ary quadrature amplitude modulation (QAM) schemes that perform well when the receiver phase-locked loop (PLL) tracks the instantaneous signal phase with moderate phase error. We propose implementations of 8- and 16-QAM transmitters using Mach-Zehnder (MZ) modulators. We outline a numerical method for computing the bit error rate (BER) of 8- and 16-QAM in the presence of AWGN and phase error. It is found that these schemes can tolerate phase-error standard deviations of 2.48/spl deg/ and 1.24/spl deg/, respectively, for a power penalty of 0.5 dB at a BER of 10/sup -9/. We propose a suitable PLL design and analyze its performance, taking account of laser phase noise, AWGN, and propagation delay within the PLL. Our analysis shows that the phase error depends on the constellation penalty, which is the mean power of constellation symbols times the mean inverse power. We establish a procedure for finding the optimal PLL natural frequency, and determine tolerable laser linewidths and PLL propagation delays. For zero propagation delay, 8- and 16-QAM can tolerate linewidth-to-bit-rate ratios of 1.8/spl times/10/sup -5/ and 1.4/spl times/10/sup -6/, respectively, assuming a total penalty of 1.0 dB.     

Dual-CRC polar codes and dual-SCFlip decoding algorithm for cell search in 5G system

Polar codes become the coding scheme for control channels of enhanced mobile broadband (eMBB) scenarios in the fifth generation (5G) communication system due to their excellent decoding performance. For the cell search procedure in 5G system, some common information bits ( CIBs) are transmitted in consecutive synchronization signal blocks ( SSBs). In this paper, a dual-cyclic redundancy check ( dual-CRC) aided encoding scheme is proposed, and the corresponding dual-successive cancellation flip ( dual-SCFlip) algorithm is given to further improve the performance of polar codes in the low signal-to-noise ratio ( SNR) environment. In dual-CRC aided encoding structure, the information bits of polar codes in different transmission blocks add cyclic redundancy check (CRC) sequences respectively according to CIBs and different information bits (DIBs). The structure enlarges the size of CIBs to improve the block error ratio ( BLER) performance of the system. The dual-SCFlip decoder can perform bit flip immediately once CIBs is decoded completely, and then decode DIBs or terminate decoding in advance according to the CRC result, which reduces the delay of decoding and mitigates the error propagation effect. Simulation results show that the dual-CRC aided encoding scheme and dual-SCFlip decoder have significant performance improvement compared to other existing schemes with low SNR.     

Transform domain inter-block interleaving schemes for robust image and video transmission in ATM networks

Data interleaving schemes have proven to be an important mechanism in reducing the impact of correlated network errors on image/video transmission. Current interleaving schemes fall into two main categories: (a) schemes that interleave pixel intensity values and (b) schemes that interleave JPEG/MPEG transform blocks. The schemes in the first category suffer in terms of lower compression ratio since highly correlated information in the spatial domain is de-correlated prior to compression. The schemes in the second category interleave DCT transformed blocks. In this case, in the absence of ARQ, if a packet is lost, an entire block may be lost thus yielding poor image quality and making the error concealment task difficult. Interleaving transform coefficients is tricky and error concealment in the presence of lost coefficients is challenging. In this paper, we develop three different interleaving schemes, namely Triangular, Quadrant, and Coefficient, that interleave frequency domain transform coefficients. The transform coefficients within each block are divided into small groups and groups are interleaved with the groups from other blocks in the image, hence they are referred to as inter-block interleaving schemes. The proposed schemes differ in terms of group size. In the Triangular interleaving scheme AC coefficients in each block are divided into two triangles and interleaving is performed among triangles from different blocks. In the Quadrant interleaving scheme, coefficients in each block are divided into four quadrants and quadrants are interleaved. In the Coefficient interleaving scheme, each coefficient in a block is a group and it is interleaved with the coefficients in other blocks. The compression ratio 3 of the proposed interleaving schemes is impressive ranging from 90 to 98% of the JPEG standard compression while providing much higher robustness in the presence of correlated losses. We also propose two new variable end-of-block (VEOB) techniques, one based on the number of AC coefficients per block (VAC-EOB) and the other based on the number of bits per block (VB–EOB). Our proposed interleaving techniques combined with VEOB schemes yield significantly better compression ratios compared to JPEG (2–11%) and MPEG-2 (3–6.7%) standards while at the same time improve the resilience of the coded data in the presence of transmission errors.     

Selected Mapping Technique for PAPR Reduction Without Side Information Based on m-Sequence

Selected mapping (SLM) is a technique for reducing the high peak-to-average power ratio (PAPR) in which a suitable signal is selected among a set of alternative signals which all indicate alike information. The chief drawback existing in this method is that transmitter is compelled to send several additional bits called side information (SI) for each data block in order that recovering at the receiver side can be possible. In this paper, we present a novel SLM scheme by using the linear feedback shift register circuit and m-sequence named MSLM technique by which any side information bit is not explicitly sent. In MSLM, The basic idea is to fit the side information into transmitted symbols based upon which some special locations in the transmitted data block are expanded, i.e. some transmitted symbols are extended. In the receiver side, by using some properties of m-sequence the SI bits can be detected. We present the example of our method for an OFDM system through the use of 16-QAM modulation and different m-sequences and finally, concerned results are illustrated from the view point of bit error rate, probability of detection failure and PAPR reduction.     

Embedding Data Into Pictures by Modulo Masking

Three systems are proposed for embedding data into industrial quality monochrome analog pictures. The video signal on each scan line is sampled, and a data bit is inserted into a block of three or five pels by modulo masking scrambling the luminance level of only one pel in the block. Prior to transmission, the combined data and video sequence is converted into a continuous signal with a bandwidth that is no greater than that of the original video signal. Using six images each containing 65 536 pels, Systems 1 and 2 embedded an average of 17 430 and 8713 bits per image, while System 3 accommodated data at a constant rate of 21 760 bits/image. The data embedding procedures of Systems 1, 2, and 3 operated with average picture SNR's of 41, 44, and 30 dB, respectively, when the transmission channel was ideal. When the transmission was over a channel composed of a second-order Butterworth filter plus additive noise that yield a channel SNR of 40 dB, no bit errors occurred but System 3 offered the greater safety margin to bit errors than Systems 1 and 2.     

OFDM-based turbo-coded hierarchical and non-hierarchicalterrestrial mobile digital video broadcasting

The feasibility of terrestrial digital video broadcast (DVB) to mobile receivers is studied and turbo coded performance enhancements are proposed. Initially, the MPEG-2 codec is subjected to a rigorous bit error sensitivity investigation, in order to assist in designing various error protection schemes for wireless DVB transmission. The turbo codec is shown to provide signal-to-noise ratio (SNR) performance advantages in excess of 5-6 dB over conventional convolutional coding both in terms of bit error rate and video quality. Our experiments suggested that-despite our expectations-multi-class data partitioning did not result in error resilience improvements, since a high proportion of relatively sensitive video bits had to be relegated to the lower integrity subchannel, when invoking a powerful low-rate channel codec in the high-integrity protection class. Nonetheless, DVB transmission to mobile receivers is feasible, when using turbo-coded OFDM transceivers at realistic power-budget requirements under the investigated highly dispersive fading channel conditions. It is interesting to note furthermore that the 5-6 dB SNR improvement due to turbo coding allows us to invoke for example the double-throughput 16-level quadrature amplitude modulation (16-QAM) mode instead of the standard convolutional-coded 4-QAM mode. This facilitates doubling the bit rate and hence improving the video quality     

Determination of best shortened linear codes

The quality of a block code is determined by its capability to protect data against undetectable errors and by the number of check bits that are required for that purpose. For a given number of check bits there are codes with optimum bit error detecting capability in shortened block lengths. These codes are determined and tabulated. The residual error characteristics of some of the tabulated codes are compared with those specified in ISO/CCITT or IEC standard data transmission protocols. For block lengths and bit error rates that are typical in process control applications, the residual error rate of the determined codes is more than six orders of magnitude smaller than that of codes specified by widely used standard transmission protocols     

Effect of coding in digital microcellular personal communicationsystems with co-channel interference, fading, shadowing, and noise

An analytical model is developed for the performance of a microcellular radio network in the presence of cochannel interference and additive white Gaussian noise. The modulation schemes considered are binary phase-shift keyed (BPSK), binary frequency-shift keyed (BFSK), and quadrature phase-shift keyed (QPSK). The multiple-access channel is statistically modeled by one Rician-distributed desired signal and several uncorrelated Rayleigh plus log-normally shadowed interfering signals, propagating according to dual path loss law with a turning point. The performance is determined in terms of bit error rate (BER), outage probability, block error probability, crosstalk probability, and spectrum efficiency, considering both fast and slow multipath fading. The effect of error correction codes, consisting of blocks with equal number of bits, on the performance parameters is also studied. The computational results show that the propagation loss exponents, Rician factor, turning point, and cell size all plays a major role in the design of an efficient microcellular system     

Decoder-assisted frame synchronization for packet transmission

This paper proposes a novel frame synchronization methodology for packets with convolutionally encoded data. Rather than by placing sync bits in a separate header, the sync bits are placed in a midamble and encoded as part of the data sequence, using the error correction encoder to resolve time ambiguities. The scheme is based on the principle that an error in trellis termination may result in decoding a wrong information bit sequence, while the starting portion of the sequence can be decoded as error free. This frame synchronization technique is extended to the synchronization of turbo-coded systems using a list-based approach, where the first synchronizer provides a list of potential packet starting positions, and the following synchronizer makes the final decision. The performance improvement over conventional synchronization techniques is quantified via simulation     

A method to analyze performance of digital connections

A comprehensive performance analysis method that models, at bit level, the error performance of individual links in an end-to-end connection is presented. The link model accounts for the burst-error behaviour of each individual link. A method to concatenate several individual links and extract a model for the end-to-end connection is given. This resulting end-to-end model can be used to calculate performance measures such as bit error rate and block error rate for any given block size. A procedure to compute the probability distribution of errors within a specific block is also developed. Finally, a method to compute the probability distribution of blocks having a certain error rate over a given period of time is presented. The utility and power of the model are illustrated with the help of an example connection     

The Design of a High-Performance Error-Correcting Coding Scheme for the Canadian Broadcast Telidon System Based on Reed-Solomon Codes

Error correction can greatly improve the performance and extend the range of broadcast teletext systems. In this paper, the requirements for an error-correcting scheme for broadcast teletext in North America (NABTS) are set down. An error-correction scheme which meets all these requirements is then described. The simplest case employs the one parity bit in each 8 bit byte and no suffix of parity check bits at the end of each data block. The next level also uses a single byte of parity check bits at the end of each data block. Adding a second byte of parity checks at the end of each data block results in a Reed-Solomon code, called theCcode, for each data block. Adding one data block of parity checks afterh - 1data blocks results in a set ofhdata packets being encoded into a bundle, in which verticalCcodes provide powerful interleaving. In a final alternative, two data blocks hold the check bytes for the vertical codewords, and the most powerful coding scheme, the double bundle code, results. The detailed mathematical definitions of the various codes are referred to or described, formulas for performance calculations are referred to, and performance curves are presented for the AWGN channel as well as for measured field data. These performance curves are discussed and compared to the performance of a difference set cyclic code, originally designed for the Japanese teletext system, which corrects any 8 bits in error in a packet.     

A Burst-Mode Bit-Synchronization IC With Large Tolerance for Pulse-Width Distortion for Gigabit Ethernet PON

A burst-mode bit-synchronization IC applied to the upstream transmission in a gigabit Ethernet passive optical network (PON) was experimentally verified to have a large tolerance for pulse-width distortion within plusmn0.66 UI. The extra tolerance of 0.22 UI over the IEEE 802.3ah specification can be assigned to additional distortion generated at an optical receiver incorporated into an optical line terminal. Such a large tolerance was attained by precisely generated eight-phase clocks based on theoretical analyses of distortion tolerance considering real circuit parameters and by an enhanced data selector incorporating a pulse-width detector to monitor the pulse-widths of isolated bits. The IC developed includes a burst into series transformer to permit connection to commercially available PON LSI developed for serial data transmission in Ethernet systems. The theoretical study into the numbers of allowable bit errors and consecutive pattern matches in byte synchronization established following two conditions: 1) allowable error more than one bit in synchronization pattern with 10-bit length was required to hold the synchronization loss rate to less than a few times per year and 2) consecutive pattern matching more than twice was required to hold the synchronization error rate to less than a few times per year     

块级篡改定位的JPEG图像脆弱水印

 JPEG是一种常见的图像格式,在JPEG图像中进行准确的篡改定位具有重要意义. 本文提出一种新的JPEG图像脆弱水印方案,将每个小块主要内容的Hash比特重新分组,并将每组的模2和作为水印信息. 也就是说每一个小块都对应多个水印比特,每个水印比特也对应多个小块. 载体图像的每个小块中仅嵌入于1比特水印,保证了良好的隐蔽性. 认证时依据图像内容与水印比特的整体匹配情况估计篡改率,再根据每个小块对应的水印信息的被破坏程度判别该小块是否曾被篡改. 理论分析和实验结果标明该方法可以在篡改区域小于1%的情况下准确地找到所有篡改小块.     

Uplink bit combining for multiple base‐stations MIMO with applications to CoMP systems

This work considers a simple bit level combining technique, aided by robust bit reliability information, for uplink collaborating multiple‐input multiple‐output (MIMO) base‐stations (also known as macrodiversity MIMO), operating over composite Rayleigh‐lognormal fading channels. Bit reliability weights based on a robust modification of the logarithmic likelihood ratio, combined with instantaneous symbol signal‐to‐noise ratio information, are derived for different local MIMO detection schemes. This bit reliability information is used at the fusion center, together with locally detected data, for combining and producing final information bits delivered to the destination. Computer simulation results confirm that such bit level combining techniques, when used with minimum mean squared error ordered successive interference cancelation and also with sphere decoding maximum likelihood local detectors, provide significant performance improvements over non‐collaborative base‐stations systems. Performance gains are maintained even when these schemes suffer from channel estimation errors and also in the presence of space correlation. Low backhaul overhead and performance advantages make these bit level combining techniques attractive for applications in next generation cellular systems employing coordinated multi‐point (CoMP) technology, as well as for other collaborative MIMO communication schemes.Copyright © 2014 John Wiley & Sons, Ltd.