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convolutional codes and coherent sheaves

APPLICABLE ALGEBRA IN ENGINEERING COMMUNICATION AND COMPUTING 2001年第4期12卷 273-326页

作者： Lomadze, V Math Inst GE-380093 Tbilisi Georgia

We present a sheaf-theoretic setting for convolutional codes in that coherent sheaves (over a projective line) play the same role as finite-dimensional linear spaces in the theory of block codes. Using coherent sheaves (and their cohomologies), we give natural straightforward proofs of the main results on the structural properties of convolutional codes.

关键词： module linear space sheaf exact sequence cohomology convolutional code convolutional encoder complexity observability noncatastrophicity linear sequential circuit formal language Hilbert function

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Hybrid trellis coded modulation (HTCM) for visible light communications

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IET COMMUNICATIONS 2019年第1期13卷 85-92页

作者： Ndjiongue, Alain Richard Ferreira, Hendrik C. Univ Johannesburg Dept Elect & Elect Engn Sci Cnr Kingsway & Univ Rd Johannesburg South Africa

The radio frequency spectrum has become very congested and scarce. A response to this dilemma is the implementation of visible light communications (VLC) technology, which is enabled by the dramatic development of light emitting diodes (LEDs) and laser diodes (LDs). VLC has become the most popular emerging telecommunication technology. This is due to the interesting advantages that it provides, which include an unlicensed and large bandwidth, a high throughput capability and a low implementation cost. VLC needs a pivot network in medium and long distance transmissions. The amplify-and-forward scenario between the backbone network and VLC is cost-effective owing to its simplicity when compared to the decode-and-forward scenario. MPSK-CSK is a typical example of cascaded systems in AF scenario with VLC where the backbone channel utilises PSK to convey the message. In this paper, we investigate a forward error correction scheme for cascaded MPSK-CSK systems. A convolutional encoder is added to the MPSK-CSK scheme to construct the hybrid trellis coded modulation scheme. Selected 8HTCM systems using set partitioning are investigated and results for a Gaussian channel are presented. Numerical results reveal that 8HTCM achieves up to 2.129 dB of asymptotic coding gain when compared to the corresponding un-coded MPSK-CSK system.

关键词： light emitting diodes forward error correction trellis coded modulation phase shift keying free-space optical communication semiconductor lasers amplify and forward communication decode and forward communication convolutional codes radio spectrum management radio frequency spectrum VLC light emitting diodes laser diodes high-throughput capability low-implementation cost pivot network long-distance transmissions backbone network AF scenario forward error correction scheme selected 8HTCM systems visible light communication technology telecommunication technology HTCM backbone channel cascaded MPSK-CSK system M-aray phase-shift-keying-colour-shift-keying mapping medium-distance transmissions decode-and-forward scenario amplify-and-forward scenario convolutional encoder hybrid trellis coded modulation scheme set partitioning Gaussian channel asymptotic coding gain uncoded MPSK-CSK system

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2D IMAGE TRANSMISSION USING BANDWIDTH EFFICIENT MAPPING TECHNIQUE

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INTERNATIONAL JOURNAL OF IMAGE AND GRAPHICS 2010年第4期10卷 559-573页

作者： Kulkarni, Shivali D. Naik, Ameya K. Nagori, Nitin S. Mumbai Univ DJ Sanghvi Coll Engn Dept Elect & Telecommun Engn Bombay 400056 Maharashtra India Mumbai Univ KJ Somaiya Coll Engn Dept Elect & Telecommun Engn Bombay 400077 Maharashtra India

Transmitting images over the wireless channel require that optimum compression ratio be maintained along with good image quality. This becomes a critical issue especially at higher values of bit error rate (BER). Joint photographic experts group (JPEG) standard and its successor JPEG 2000 provide excellent compression ratio but image reconstruction becomes highly difficult under extreme noise conditions. We present a mapping technique which gives better compression as compared to the existing techniques. Also, its performance is excellent even for higher bit error rates (BERs). This is supported by the results presented for JPEG, JPEG 2000, as well as mapping technique under fading channel conditions. Moreover, it is observed that the presence of high levels of noise has negligible effect on the reconstruction of images encoded using mapping technique.

关键词： convolutional encoder discrete cosine transform JPEG standard JPEG 2000 mapping technique Rician channel

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Combined channel estimation and data decoding based on fuzzy logic

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2002年第2期51卷 342-346页

作者： Byun, YB Takama, Y Hirota, K Univ Seoul Seoul South Korea Tokyo Inst Technol Interdisciplinary Grad Sch Sci & Engn Dept Computat Intelligence & Syst Sci Tokyo 152 Japan

A simple method that detects the data sequence and at the same time estimates the channel condition is proposed using the Viterbi algorithm and fuzzy logic for the convolutional code. After a fixed number of decoding steps, the fuzzy logic unit reads the branch metric value of the survivor and the difference between maximum and minimum survivor path metric values at the Viterbi decoder and estimates the channel condition with the signal-to-noise ratio. The proposed method enables the channel estimation regardless of what kinds of modulator and demodulator are used. In the experiment, constraint length 7 and code rate 1/2 convolutional code that is standardized by the European Space Agency (ESA) is used. The effective movement range of the proposed channel estimation method is from 0.0 dB to 25 dB.

关键词： channel estimation communication system convolutional encoder fuzzy logic fuzzy modeling Viterbi decoding algorithm

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A Reduced Complexity Algorithm of the Butterfly Trellis Unit for the Viterbi Decoder

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JOURNAL OF AERONAUTICS ASTRONAUTICS AND AVIATION 2022年第2期54卷 147-159页

作者： Rashid, Ruhaida Abdul Harun, Harlisya Ayob, Mohd Zaki Shamsudin, Norfadilah Nor, Sahzilawati Mohamed UniKL MIAT Satellite Commun & Av Syst Integrat SCASI Res Lab Avion Sect Lot 2891Jalan Jenderam Hulu Dengkil 43800 Selangor Malaysia Univ Kuala Lumpur British Malaysian Inst UniKL BMI Batu 8Jalan Sungai Pusu Bangi 53100 Selangor Malaysia

Together with convolutional encoders, Viterbi decoders are commonly used to provide an excellent probability of error correction in wireless transmission. The encoder constraint length k must be set at higher values to achieve an improved bit error rate. With the growth of the Internet of Things (IoT) in recent years, there is inevitable demand for low-power IoT applications. Unfortunately, an increase in the value of k causes the complexity of the algorithm to increase exponentially. Consequently, the Viterbi decoder's power consumption will increase exponentially, which is a detriment to many wireless communication devices. Many of the Viterbi decoder's reduced complexity decoding approaches discussed in the past concentrated on the particular level of algorithms and architectures. Most of the studies focused on the difficulty of the decoder's Add-Compare Select Unit (ACSU) repetitive processing. This paper analyzes many variations carried out in the ACSU of the Viterbi algorithm. Several separate algorithms were compared and an approach to a combined algorithm was suggested. This paper offered an in-depth description of the reduced computation and its design for the proposed algorithm. Each algorithm and reduced complexity are compared with the conventional VD. The impact of power consumption is evaluated through the bit-error-rate (BER) vs Signal-to-Noise ratio (SNR), such that the proposed algorithm was found to have the best dB gain between 0 dB and 5 dB, indicating a significant power improvement over the other algorithms.

关键词： Adaptive Viterbi decoder Adaptive M-algorithm convolutional encoder M-algorithm Viterbi algorithm

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MODELING OF ADS-B DATA TRANSMISSION VIA SATELLITE

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AVIATION 2013年第3期17卷 119-127页

作者： Kharchenko, Volodymyr Barabanov, Yuri Grekhov, Andrii Natl Aviat Univ Air Nav Syst Dept Air Nav Inst Kosmonavta Komarova Ave 1 UA-03680 Kiev Ukraine

For modelling transmission of ADS-B messages via low-orbit satellite constellation Iridium, the original model of a communication channel "Aircraft-to-Satellite-to-Ground Station" was built using MATLAB Simulink. The model comprises "Aircraft Uplink Transmitter" (Bernoulli Random Binary Generator, convolutional encoder, BPSK Baseband Modulator, High Power Amplifier with a memoryless nonlinearity, Transmitter Dish Antenna Gain), "Uplink Path" (Free Space Path Loss, Phase/Frequency Offset), "Satellite Transponder" (Receiver Dish Antenna Gain, Satellite Receiver System Temperature, Complex Baseband Amplifier, Phase Noise, Transmitter Dish Antenna Gain), "Downlink Path" (Free Space Path Loss, Phase/Frequency Offset), "Ground Station Downlink Receiver" (Receiver Dish Antenna Gain, Ground Receiver System Temperature, Viterbi Decoder), "Error Rate Calculation" block and "Display". The modelling was realized without and with convolutional coding (r = 3/4, K = 7) at different noise temperatures and free space losses. Dependencies of a Bit Error Rate on free space path losses, antenna's diameter, phase/frequency offsets, satellite transponder linear gain, aircraft and satellite transponder high power amplifier back-off level, and phase noise were received and analysed.

关键词： ADS-B BER communication channel aircraft satellite transponder ground station convolutional encoder BPSK free space loss phase/frequency offset memoryless nonlinearity phase noise Viterbi decoder amplifier backoff level noise temperature antenna diameter

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CORDIC Based Reconfigurable Architecture for DSCDMA/CI Transmitter

CORDIC Based Reconfigurable Architecture for DSCDMA/CI Trans...

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3rd IEEE Students' Technology Symposium (IEEE TechSym)

作者： Kapoor, Rajan Sundar, S. Shyam Kumar, Preetam IIT Patna Dept Elect Engn Patna Bihar India

ISBN: (纸本)9781479926084

The traditional model of DS-CDMA transmitter is not efficient when spreading codes are complex since complex multiplications needed for spreading would consume more power, require more area for implementation and incur more delays. In this paper, a novel architecture for DS-CDMA/CI transmitter is proposed which uses CORDIC algorithm to generate carrier whose phase offset is controlled by Carrier Interferometry (CI) codes. The architecture is based on the principle that product of two exponential is essentially an exponential with angle equal to sum of angle of product components. Furthermore, the architecture is reconfigurable in the sense that the spreading codes can be dynamically assigned during transmission and therefore can be used for designing communication systems for cognitive radio applications. The maximum frequency of operation was found to be 22 MHz from timing analysis results for given model for SPARTAN 3E FPGA.

关键词： BPSK modulator convolutional encoder CORDIC DS-CDMA/CI FPGA

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Error probabilities for radio transmissions of MC-CDMA based W-LANs

Error probabilities for radio transmissions of MC-CDMA based...

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61st IEEE Vehicular Technology Conference

作者： Orfanos, G Habetha, J Butsch, W Rhein Westfal TH Aachen Aachen Germany

ISBN: (纸本)0780388879

IEEE 802.11a/e has become a worldwide wireless local area network (W-LAN) standard, with a rapid development. Many proposals have been made for its further expansion, and some of them focus on multicarrier code division multiple access (MC-CDMA), a novel, high capacity, multicarrier modulation scheme. In this paper we present an analysis of the error models for radio transmissions in such systems. An accurate model of the channel is necessary for the performance evaluation of the protocol by means of computer simulations. Focusing on the estimation of the signal to interference and noise ratio (SENR) at the detector and on the calculation of a packet error ratio (PER), in this contribution we discuss a modeling approach which allows an efficient calculation of frame transmissions over a MC-CDMA shared radio channel.

关键词： component IEEE 802.11a/e MC-CDMA radio channel modeling MMSE PER convolutional encoder

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Cryptographic Turbo Code for Image Transmission over Mobile Networks 5

Cryptographic Turbo Code for Image Transmission over Mobile ...

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International Conference on Advances in Computing, Communications and Informatics (ICACCI)

作者： Sawant, Vidya Bhise, Archana NMIMS Univ Mukesh Patel Sch Technol Management & Engn Bombay Maharashtra India

ISBN: (纸本)9781509020287

Mobile communication has become an essential part of our daily life for accessing and sharing data over internet in addition to voice communication. Mobile communication channel is an open network and hence maintaining the confidentiality and reliability of the data has always been an area of concern. Reliability of data against channel noise can be ensured by various error correcting codes. Turbo Code (TC) is an excellent channel encoder with near Shannon limit error correction performance. However, TC does not guarantee the security of the transmitted image against intruders on the wireless channel. Proposed Cryptographic Turbo Code (CTC) is a modification of the existing TC to provide encryption and error correction as a single entity. Encryption of data is achieved by the proposed Elliptic Curve Cryptographic Interleaver (ECCI) of CTC. The ECCI is an asymmetric private key interleaver which shuffles the input bit sequence based on the Elliptic Curve (EC) arithmetic and a private key. Shuffling the bits also reduces its correlation and improves the error correction performance of the code. The CTC ensures the secrecy of the shared private keys over an insecure wireless channel by Elliptic Curve Diffie-Hellman Key Exchange (ECDHKE). This makes the CTC robust against cryptographic attacks. The qualitative and quantitative performance analysis of the proposed code is evaluated to validate its effectiveness for image transmission over a mobile network in contrast to other state-of-art methods. Simulation results illustrate a similar coding gain, Peak Signal to Noise Ratio (PSNR) and Mean Square Error (MSE) for images retrieved by the proposed CTC, encrypted TC and TC for authorized users. Additionally, it ensures security of the data from unauthorized users as compared to TC. Investigation results also depict the strength of CTC against Brute Force, known plaintext, chosen plaintext and cipher text attacks.

关键词： Bit error rate cryptographic turbo code convolutional encoder elliptical curve cryptographic interleaver

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A Reconfigurable Viterbi Decoder for SDR and Mobile Communications

A Reconfigurable Viterbi Decoder for SDR and Mobile Communic...

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International Conference on High Performance Computing and Applications (ICHPCA)

作者： Pradhan, Ashish Kumar Nandy, S. K. Indian Inst Sci CeNSE Bangalore Karnataka India Indian Inst Sci SERC Bangalore Karnataka India

ISBN: (纸本)9781479959587

Data rate grows monotonously in every new generation of wireless communication system and so does the error rate while transmitting through wireless channels. Hence channel coding, error detection and correction play a major role in overall system performance. Unlike Blockcodes, convolutional code (CC) offers high error resiliance capacity by increasing their constraint length, instead of increasing the code redundancy. Viterbi decoders have been widely used as the decoder for convolutional codes. In this paper we present a dynamically reconfigurable Viterbi Decoder (VD). The proposed Viterbi decoder supports code rates of 1/2, 1/3,2/3,3/4,5/6, constraint lengths from 3-9, and arbitrary block lengths. The proposed decoder is synthesized in ISE and implemented on Xilinx XCV330T device. A throughput of 197 Mbps is achieved at frequency 197 MHz, which shows the architecture to be superior in terms of reconfiguration and throughput to reconfigurable Viterbi decoders on FPGA platform published in literature.

关键词： convolutional encoder Viterbi Decoder Channel Decoder Reconfigurable Configurable Switch

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