Serial Concatenated Convolutional Codes Research Articles

Design and Development of a CCSDS 131.2-B Software-Defined Radio Receiver Based on Graphics Processing Unit Accelerators

In recent years, the number of Earth Observation missions has been exponentially increasing. Satellites dedicated to these missions usually embark with payloads that produce large amount of data and that need to be transmitted towards ground stations, in time-limited windows. Moreover, the noisy nature of the link between satellites and ground stations makes it hard to achieve reliable communication. To address these problems, a standard for a flexible advanced coding and modulation scheme for high-rate telemetry applications has been defined by the Consultative Committee for Space Data Systems (CCSDS). The defined standard, referred to as CCSDS 131.2-B, makes use of Serially Concatenated Convolutional Codes (SCCC) based on 27 ModCods to optimize transmission quality. A limiting factor in the adoption of this standard is represented by the complexity and the cost of the hardware required for developing high-performance receivers. In the last decade, the performance of software has grown due to the advancement of general-purpose processing hardware, leading to the development of many high-performance software systems even in the telecommunication sector. These are commonly referred to as Software-Defined Radio (SDR), indicating a radio communication system in which components that are usually implemented in hardware, by means of FPGAs or ASICs, are instead implemented in software, offering many advantages such as flexibility, modularity, extensibility, cheaper maintenance, and cost saving. This paper proposes the development of an SDR based on NVIDIA Graphics Processing Units (GPU) for implementing the receiver end of the CCSDS 131.2-B standard. At first, a brief description of the CCSDS 131.2-B standard is given, focusing on the architecture of the transmitter and receiver sides. Then, the receiver architecture is shown, giving an overview of its functional blocks and of the implementation choices made to optimize the processing of the signal, especially for the SCCC Decoder. Finally, the performance of the system is analyzed in terms of data-rate and error correction and compared with other SW systems to highlight the achieved improvements. The presented system has been demonstrated to be a perfect solution for CCSDS 131.2-B-compliant device testing and for its use in science missions, providing a valid low-cost alternative with respect to the state-of-the-art HW receivers.

Area and Energy Efficient QCA Based Compact Serial Concatenated Convolutional Code Encoder

Quantum-dot Cellular Automata (QCA) is a transistor-less technology known for its low power consumption and higher clock rate. Serial Concatenated Convolutional Coding (SCCC) encoder is a class of forward error correction. This paper picturizes the implementation of the outer encoder as a (7, 4, 1) Bose Chaudhary Hocquenghem encoder that serves the purpose of burst error correction, a pseudo-random inter-leaver used for permuting of systematic code words and finally the inner encoder which is used for the correction of random errors in QCA. Two different architectures of the SCCC encoder have been proposed and discussed in this study. In the proposed two architectures, the first based on external clock signals whereas the second based on internal clock generation. The sub-blocks outer encoder, pseudo-random inter-leaver and inner encoder of the SCCC encoder are optimized, implemented and simulated using QCADesigner and then integrated to design a compact SCCC encoder. The energy dissipation is computed using QCADesigner-E. The proposed SCCC encoder reduced the total area by 46% and energy dissipation by 50% when compared to the reference SCCC encoder. The proposed encoders are more efficient in terms of cell count, energy dissipation and area occupancy respectively.

P.107 The effects of sleep on behavioural, cardiovascular and central measures of fear conditioned response

Quantum-dot cellular automata (QCA) are a prospective nanotechnology with striking performance for complementing complementary metal oxide semiconductor (CMOS) based integrated circuit technique. For applications in communications, serial concatenated convolutional codes (SCCCs) have been investigated due to their negligible error floor for deep space communication. Using a combination of top-down and bottom-up approaches, we design and implement an SCCC encoder in QCA technology. In this work, a Bose–Chaudhuri–Hocquenghem (BCH) code encoder with the ability for correcting burst errors, a pseudo random interleaver for permuting signal bits, and a convolutional code encoder for correcting random errors are logically connected in series for composing the SCCC encoder. Specifically, inspired by the idea for a divider design, a layout for (n, k, t) BCH code encoders is proposed and implemented with QCA cells. For using the four-phase clock mechanism, we also devise the serial-to-parallel and parallel-to-serial converters for constructing the interleaver. In addition, (u, f, K) convolutional code encoders with various constraint lengths are designed as well. The functionalities and validity of the proposed circuit design are verified by using QCADesigner.

CCSDS 131.2-B-1 telemetry transmitter: A VHDL IP core and a validation architecture on board RTG4 FPGA

During the last years, improvement in the resolution of Earth observation satellite instruments has been leading to the necessity of high throughput transmitters, featuring efficient encoding and modulation schemes. For that reason, the Consultative Committee for Space Data Systems (CCSDS) issued the CCSDS 131.2-B-1 standard describing the architecture of a flexible telemetry transmitter featuring Serially Concatenated Convolutional Codes (SCCCs). Such flexibility allows CCSDS 131.1-B-1 implementations to take full advantage of the channel by dynamically changing the coding-rate and type of modulation (Adaptive Code and Modulation, ACM).This work presents a VHDL Telemetry Transmitter IP Core fully compliant to the CCSDS 131.2-B-1 standard. The IP Core is technology independent and as such can be fitted on different Field Programmable Gate Arrays (FPGAs), including space grade devices, realizing a broad spectrum of solutions that differ in terms of transmission throughput, radiation hardness and cost figures. In particular, this work shows that the IP Core is able to reach 259.3 Mbaud and 1355 Mbit/s data transfer on the Microsemi RTG4 FPGA. To verify the IP Core functionalities on board the different FPGAs, register-transfer level (RTL) and post-layout simulations were performed through a custom verification environment. The latter allowed 100% functional and code coverage according to a dedicated test plan. Finally, the IP was validated through an appropriate validation system on board the Microsemi RTG4 FPGA exploiting a hardware/software co-design approach.

Serial concatenated convolutional code encoder in quantum-dot cellular automata

Quantum-dot cellular automata (QCA) are a prospective nanotechnology with striking performance for complementing complementary metal oxide semiconductor (CMOS) based integrated circuit technique. For applications in communications, serial concatenated convolutional codes (SCCCs) have been investigated due to their negligible error floor for deep space communication. Using a combination of top-down and bottom-up approaches, we design and implement an SCCC encoder in QCA technology. In this work, a Bose–Chaudhuri–Hocquenghem (BCH) code encoder with the ability for correcting burst errors, a pseudo random interleaver for permuting signal bits, and a convolutional code encoder for correcting random errors are logically connected in series for composing the SCCC encoder. Specifically, inspired by the idea for a divider design, a layout for (n, k, t) BCH code encoders is proposed and implemented with QCA cells. For using the four-phase clock mechanism, we also devise the serial-to-parallel and parallel-to-serial converters for constructing the interleaver. In addition, (u, f, K) convolutional code encoders with various constraint lengths are designed as well. The functionalities and validity of the proposed circuit design are verified by using QCADesigner.

Channel State based Adaptive Modulation and Coding for High Bit-Rate Telemetry Applications

This paper defines associate efficient and comprehensive cryptography and modulation resolution able to support a good vary of spectral efficiency values and knowledge rates in conjunction with high out turn. The most target is given by high rate measure applications, i.e., Earth Exploration Satellite Service (EESS) measure payload, wherever the rise of the system out turn by means that of advanced adaptive techniques is deemed essential so as to fulfill the necessities obligatory by future missions. This paper discusses the matter of adaptive modulation theme choice through an efficient realization of Orthogonal Frequency Division Multiplexing (OFDM) primarily based system in conjunction with Serial Concatenated Convolutional Code (SCCC) guarantee a really low error chance. Additionally this theme makes use of Digital Video Broadcasting Second Generation (DVB-S2) customary to produce giant form of modulation techniques and different cryptography rates. Overall, this permits the system to form efficient use of the accessible information measure, adapting itself to the variable conditions of the link.

Some Extended Results on the Design of Punctured Serially Concatenated Convolutional Codes

The aim of this paper is twofold. On one hand, it presents the results of the search for good punctured systematicrecursive convolutional encoders suitable for application in serially concatenated convolutional codes (SCCCs) operating in two different target regions: at low-to moderate signal-to-noise ratios (SNRs), i.e., in the so called waterfall region, and at high SNRs. On the other hand, it provides some useful design guidelines for choosing the constituent encoders in an SCCC. The results of the search for good SCCCs operating in the waterfall region rely upon an effective algorithm, based on density evolution technique, first proposed in a companion paper. Good punctured SCCCs were obtained through considerationsdeduced by the behaviour of the bit error probability of an SCCC for high values of both SNR and interleaver length, i.e., through asymptotic considerations. The mother codes in the serial concatenation are rate 1/2 recursive convolutional encoders (RCC) found by an exhaustive search for encoders tailored to SCCC schemes, using two different selection criteria. Extensive tables of optimized puncturing patterns for various mother codes and SCCCs are presented along with sample simulation results.

Enhancement the Performance of OFDM based on Multiwavelets Using Turbo Codes

In wireless communication systems, the main challenge is to provide a high data rate and reliable transmission over a frequency selective fading channel. Orthogonal Frequency Division Multiplexing (OFDM) is a very attractive technique for high data rate transmission with better bandwidth efficiency. In this paper, the effectiveness of turbo codes is utilized to develop a new approach for an OFDM system based on a Discrete Multiwavelet Critical-Sampling Transform (OFDM-DMWCST). The use of turbo coding in an OFDM-DMWCST system is useful in providing the desired performance at higher data rates. Two types of turbo codes were used in this work, i.e., Parallel Concatenated Convolutional Codes (PCCCs) and Serial Concatenated Convolutional Codes (SCCCs). In both types, the decoding is performed by the iterative decoding algorithm based on the log-MAP (Maximum A Posteriori) algorithm. The simulation results showed that, the turbo-coded OFDM-DMWCST system achieves large coding gain with lower Bit-Error-Rate (BER), therefore, offering a higher data rate under different channel conditions. In addition, the PCCCs offer better performance than SCCCs.

Performance Analysis and Implementation of SISO Iterative Receiver for SCCC

Serial concatenated convolutional codes (SCCC) have gained a great interest in recent years for outperforming PCCC at high SNR and lower error floor. In this paper, the BER performance of SCCC based on different decoding algorithm such as Log-MAP algorithm, Max-Log-MAP algorithm and improved Max-Log-MAP algorithm are investigated. In order to achieve a flexible high throughput, low complexity and multi-rate decoding process, some improved methods are proposed.

FEC Systems for Aeronautical Telemetry

We consider the design of capacity-approaching forward error correction (FEC) systems for use in the aeronautical telemetry environment. The modulation format is the bandwidth-efficient telemetry-group version of shaped-offset quadrature phase-shift keying (SOQPSK-TG). The FEC codes are a low-density parity-check (LDPC) code and a serially concatenated convolutional code (SCCC). The block structure of the two types of FEC is designed such that the two code words are formatted as similarly as possible. This unified format allows the flexibility of the FEC-encoded signal to be received by legacy test-range assets that are not equipped with FEC?although no coding gain is realized in such a case. We also show how a wide range of near-optimal SOQPSK demodulators can be paired with the FEC decoders; this includes the most widely deployed SOQPSK demodulator (the so-called symbol-by-symbol (SxS) demodulator), which so far has not been considered for use in FEC applications. In all of our demodulator/decoder designs, we apply techniques that are simple and robust and that fully decouple the demodulator's tasks (e.g., synchronization, filtering) from the decoder's tasks (e.g., path metrics, soft outputs). For both LDPC and SCCC, we show that very attractive system designs can perform within 0.5 dB of optimum, while requiring only a fraction of the complexity of the optimum system.

Performance Enhancement of SOVA Based Decoder in SCCC and PCCC Schemes

This study proposes a simple scaling factor approach to improve the performance of parallel-concatenated convolutional code (PCCC) and serial concatenated convolutional code (SCCC) systems based on suboptimal soft-input soft-output (SISO) decoders. Fixed and adaptive scaling factors were estimated to mitigate both the optimistic nature of a posteriori information and the correlation between intrinsic and extrinsic information produced by soft-output Viterbi (SOVA) decoders. The scaling factors could be computed off-line to reduce processing time and implementation complexity. The simulation results show a significant improvement in terms of bit-error rate (BER) over additive white Gaussian noise and Rayleigh fading channel. The convergence properties of the suggested iterative scheme are assessed using the extrinsic information transfer (EXIT) chart analysis technique.

Analysis of WiMAX Performance Improvement Using Serial and Parallel Concatenated Convolutional Codes

This paper is proposed for analysis of WiMAX performance improvement by coding and iterative decoding algorithms. Forward error correction (FEC) is one of the most important sections in physical layer of WiMAX system. IEEE802.16 standard has offered several types of FEC for WiMAX e.g. Reed Solomon and Convolutional Code (RS-CC). This paper offers using of two kinds of Turbo codes, Serial and parallel concatenated convolutional codes (SCCCs and PCCCs) with suitable parameters as FEC for WiMAX. Simulations are carried out for RS-CC, SCCC and PCCC. BPSK and 64QAM are selected as modulation schemes in simulations. Simulation results show that the use of SCCC and PCCC has better performance than RS-CC because of their superior coding and iterative decoding algorithm in this work.

Performance Comparison of Serial Concatenated Convolutional Codes and Parallel Concatenated Convolutional Codes on Faded Channels

The performance comparison of Serially Concatenated Convolutional Codes (SCCC) and Parallel Concatenated Convolutional Codes (PCCC) is evaluated on Additive White Gaussian Noise model channel, which is used as a basis, and actions of SCCC and PCCC on Raleigh faded channels are evaluated in this research work. In DCS the SCCC and PCCC are utilized to reduce the bit error rates. SCCC and PCCC encoder consists of RSCC. The major thrust is iterative decoding. This research has utilized BCJR and TDA decoding algorithms. This research analyzed SCCC and PCCC with interleaved scheme. The BPSK modulation was considered. Performance metric for SCCC and PCCC over Memory less AWGN channel, and memory based channels i.e. Rayleigh slow and fast Faded Channel is BER verses SNR.

Performance of Hybrid Concatenated Trellis Codes CPFSK with Iterative Decoding over Fading Channels

Concatenation is a method of building long codes out of shorter ones, it attempts to meet the problem of decoding complexity by breaking the required computation into manageable segments. Concatenated Continuous Phase Frequency Shift Keying (CPFSK) facilitates powerful error correction. CPFSK also has the advantage of being bandwidth efficient and compatible with non-linear amplifiers. Bandwidth efficient concatenated coded modulation schemes were designed for communication over Additive White Gaussian noise (AWGN), and Rayleigh fading channels. An analytical bounds on the performance of serial concatenated convolutional codes (SCCC), and parallel concatenated convolutionalcodes (PCCC), were derived as a base of comparison with the third category known as hybrid concatenated trellis codes scheme (HCTC). An upper bound to the average maximum-likelihood bit error probability of the three schemes were obtained. Design rules for the parallel, outer, and inner codes that maximize the interleaver's gain were discussed. Finally, a low complexity iterative decoding algorithm that yields a better performance is proposed.

Design of Optimized Convolutional and Serially Concatenated Convolutional Codes in the Presence of A-priori Information

In this paper, we focus on the design of optimized binary convolutional codes (CCs) and serially concatenated convolutional codes (SCCCs) in the presence of a-priori information (API) at the receiver. For large signal-to-noise ratios (SNRs), we first propose a CC design criterion based on the minimization of a union bound on the bit error probability (BEP). In this case, relevant performance gains, with respect to previously proposed CCs, are obtained. These gains persist even in the presence of estimation errors on the API. Then, we apply the same union bound-based design criterion to SCCCs. Since the BEP of SCCCs is characterized by a typical waterfall shape, the proposed union bound-based design criterion is accurate only at large SNR, to estimate the BEP floor. In order to complement this analysis, we propose a density evolution-based approach to optimize the SCCC design in terms of minimization of the SNR of the knee of the BEP curve. The obtained simulation results show substantial gains with respect to previously proposed parallel concatenated convolutional coding (PCCCing) schemes optimized under the assumption of no API at the decoder. Moreover, in the presence of strong API the proposed SCCCs allow to approach the Shannon limit (SL) more than any previously proposed turbo coding scheme.

Design and performance analysis of a new class of rate compatible serially concatenated convolutional codes

In this paper, a novel class of serially concatenated convolutional codes (SCCCs) is addressed. In contrast to standard SCCCs, where high rates are obtained by puncturing the outer code, the heavy puncturing is moved to the inner code, which can be punctured beyond the unitary rate. We derive analytical upper bounds on the error probability of this code structure by considering an equivalent code construction consisting of the parallel concatenation of two codes, and address suitable design guidelines for code optimization. It is shown that the optimal puncturing of the inner code depends on the outer code, i.e., it is interleaver dependent. This dependence cannot be tracked by the analysis for standard SCCCs, which fails in predicting code performance. Based on the considerations arising from the bounds analysis, we construct a family of rate-compatible SCCCs with a high level of flexibility and a good performance over a wide range of code rates, using simple constituent codes. The error rate performance of the proposed codes is found to be better than that of standard SCCCs, especially for high rates, and comparable to the performance of more complex turbo codes.

A flexible rate slepian-wolf code construction

A flexible rate Slepian-Wolf (SW) code is constructed, which is vital for wireless sensor network applications. The proposed solution is based on an efficient and practical algorithm to compute the syndrome of the rate-compatible convolutional codes (RCPC). Using this algorithm, there is no need to compute the syndrome of punctured version of the mother code for each puncturing matrix, which is complex. Instead, the syndrome of the punctured code is the punctured version of the syndrome of the mother code using the same pattern of puncturing. The algorithm is general for all convolutional codes in Zq. The strategy is also generalized for parallel and serial concatenated convolutional codes. For the cases, where the dependencies among sources are modeled as a virtual discrete channel, a simplified decoding scheme is suggested. This method is generalized to achieve all points on the SW boundary using a simple code design technique. Simulation results demonstrate the performance and effectiveness of the proposed methods.

Capacity-Achieving CPM Schemes

The pragmatic approach to coded continuous-phase modulation (CPM) is proposed as a capacity-achieving low-complexity alternative to the serially-concatenated CPM (SC-CPM) coding scheme. In this paper, we first perform a selection of the best spectrally-efficient CPM modulations to be embedded into SC-CPM schemes. Then, we consider the pragmatic capacity (a.k.a. BICM capacity) of CPM modulations and optimize it through a careful design of the mapping between input bits and CPM waveforms. The so obtained schemes are cascaded with an outer serially-concatenated convolutional code to form a pragmatic coded-modulation system. The resulting schemes exhibit performance very close to the CPM capacity without requiring iterations between the outer decoder and the CPM demodulator. As a result, the receiver exhibits reduced complexity and increased flexibility due to the separation of the demodulation and decoding functions.

On the design of rate‐compatible serially concatenated convolutional codes

AbstractA powerful class of rate‐compatible serially concatenated convolutional codes (SCCCs) has been proposed based on minimising analytical upper bounds on the error probability in the error floor region. In this paper, this class of codes is further investigated by combining analytical upper bounds with extrinsic information transfer chart analysis to improve performance in the waterfall region. Following this approach, we construct a family of rate‐compatible SCCCs with low complexity and good performance in both the error floor and the waterfall regions over a broad range of code rates. The proposed codes outperform standard SCCCs and have a similar performance as more complex parallel concatenated convolutional codes (PCCCs). The proposed codes perform particularly well for high code rates. Copyright © 2007 John Wiley & Sons, Ltd.

Turbo modulation and coding: design and evaluation of iterative bit‐interleaved coded modulation methods for wireless systems beyond 3G

AbstractWe give an overview of iterative techniques for bit‐interleaved coded modulation. We start with simple methods where a convolutional code is concatenated with a standard QAM modulation scheme. The mapping is carefully chosen different from Gray mapping such that significant gains can be obtained by an iterative (turbo) receiver. The idea can also be applied to transmit antenna diversity as well as spatial multiplexing (MIMO). We then consider various powerful iterative coding schemes which are under discussion in standardisation for wireless systems beyond 3G such as serial or parallel concatenated convolutional codes, repeat accumulate codes and LDPC codes. We give a comparison in terms of complexity and performance.The main intention is to provide an illustrative overview over relevant applications of the turbo principle in demodulation and decoding. It is a summary of results which have been obtained in collaboration between the Institute of Communications Engineering, TUM and DoCoMo Euro‐Labs. Copyright © 2007 John Wiley & Sons, Ltd.