Power Computation and Performance Analysis of Viterbi-Decoder Using FPGA

Convolutional code is a coding scheme used in communication systems including deep space communications and wireless communications.It provides an alternative approach to block codes for transmission over a noisy channel.The block codes can be applied only for the block of data.The Convolutional coding has an advantage over the block codes in that it can be applied to a continuous data stream as well as to blocks of data.Viterbi decoder employed in digital wireless communication plays a rife role in the overall power consumption of trellis coded modulation decoder.Power reduction in Viterbi decoder could be achieved by reducing the number of states.A pre-computation architecture with T-algorithm was implemented for this purpose, and when we compare this result with full Trellis Viterbi decoder, this approach significantly reduces power consumption without degrading decoding speed.Convolutional encoding with viterbi decoding is a powerful FEC technique that is particularly suited to a channel in which the transmitted signal is corrupted mainly by Additive White Gaussian Noise (AWGN).It operates on data stream and has memory that uses previous bits to encode.The Viterbi Algorithm (VA) is proposed, used for decoding a bit stream that has been encoded using FEC code.The Convolutional encoder adds redundancy to a continuous stream of input data by using a linear shift register.A pre-computation architecture with Viterbi algorithm is implemented for this purpose, Viterbi (Convolutional) encoder and Viterbi decoder are designed and implemented using FPGA technology, which are the essential blocks in digital communication systems.It is particularly suited to a channel in which the transmitted signal is corrupted mainly by AWGN.The Viterbi decoder of Constraint length 7 and code rate ½ is considered.The design is implemented using verilog on Xilinx Spartan 3E and advanced Spartan 6 board and the results and Comparisons are presented.

The puncturing technique allows obtaining high-rate convolutional codes from low-rate convolutional codes used as mother codes. This technique has been successfully applied to generate good high-rate convolutional codes which are suitable for Viterbi and sequential decoding. In this paper, we investigate the puncturing technique for convolutional self-doubly orthogonal codes (CSO/sup 2/C) which are decoded using an iterative threshold-decoding algorithm. Based on an analysis of iterative threshold decoding of the rate-R=b/(b+1) punctured systematic CSO/sup 2/C, the required properties of the rate-R=1/2 systematic convolutional codes (SCCs) used as mother codes are derived. From this analysis, it is shown that there is no need for the punctured mother codes to respect all the required conditions, in order to maintain the double orthogonality at the second iteration step of the iterative threshold-decoding algorithm. The results of the search for the appropriate rate-R=1/2 SCCs used as mother codes to yield a large number of punctured codes of rates 2/3/spl les/R/spl les/6/7 are presented, and some of their error performances evaluated.

Rapidly growing demand for high data rates in wireless communication systems is the cause of the merging of Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) techniques. MIMO-OFDM technique needs Radio Frequency (RF) front end in each antenna, which is not effective for large dimensional antenna size. Therefore, RF front end on the receiver side will be simplified using a single RF technique based on the Electrically Steerable Parasitic Array Radiator (ESPAR) antenna. In real life, a channel cannot be ideal. Therefore, before the signal is transmitted, that signal must be coded to minimized errors when the data transmission process. Convolutional code is a coding technique that can detect and correct error bit (error control coding) and that it is expected to reduce the quantity of Bit Error Rate (BER). In this research, a simulation is designed to analyze single RF performance on the MIMO-OFDM system using Vertical Bell Laboratories Space-Time (VBLAST) detection for convolutional code encoder and Viterbi decoder. The result simulation shows that the channel estimation technique works well on the MIMO-OFDM system using single RF, which is shown in the magnitude and phase curves against the subcarrier index between the theory channel and the estimated channel are at almost the same points. VBLAST-ZF detector performance is shown in the BER curve against SNR, where the difference BER value for SNR value 10 dB between the theory channel and the estimated channel is 0.001499. Channel coding technique using convolutional code encoder and Viterbi decoder with a rate of ½ works well on the MIMO-OFDM system using single RF which is shown in the BER curve against SNR, where BER value with coding technique is smaller than BER value without coding technique.

The authors propose a novel control channel quality improvement scheme for satellite communication systems using a majority decision method over convolutional coding and Viterbi decoding channels. To improve majority decision performance, which is degraded by burst errors due to Viterbi decoding in conventional serial transmission methods, a parallel transmission method is proposed. The performance of the parallel and serial transmission methods has been analyzed, and experimenta have been carried out using rate 1/2 convolutional encoding and Viterbi decoding (constraint length 4 and 7). It is shown that the parallel transmission method has about 10/sup 10/ times lower block error performance at P/sub e/=1*10/sup -4/ than the conventional method. >

Convolutional codes are channel codes, which are extensively used in communication systems like GSM (global system for mobile communications) and Interim standard IS-95.We introduce a strategy to present convolutional codes to students learning wireless communication systems, digital communication or similar courses, without using mathematical structures.In this paper, we will discuss our method to implement convolutional encoding and Viterbi decoding to determine the bit error rate.We have compared its performance under different conditions.To exemplify and illuminate our approach, we have selected a communication channel with rate 1/3 convolutional code.Constrain length is three for both Viterbi hard decision decoding method and Viterbi soft decision decoding method.Results suggest that soft decision decoding has at least 3.24 dB improvements in SNR compared to hard decision decoding for same bit error rate.Also by using soft decision Viterbi decoding on AWGN channel, we have examined various convolutional codes for four different constrain lengths and rates.We find that the first code with rate 1/3 code and constrain length 3 has better bit error rate performance with respect to other coding methods.This means, it gives a lower bit error rate for the same value of signal to noise ratio used in other coding schemes.Thus, to achieve the same bit error rate the first code will require a lower SNR.A lower SNR means a lower transmitter power.However, if we use this code the bandwidth requirement is three times larger compared with an un-coded transmission.For the second coding scheme we have an increase in bandwidth by a factor of 2 and for the third and fourth coding scheme the increase factor is 1.5.We believe this approach and its corresponding results will expose students to conceptual and technical aspects of signal encoding and its analysis.

In this paper, two novel interleaving schemes suitable for a convolutional code are given as the block interleaving scheme and bit interleaving scheme. Based on convolutional coding with Viterbi decoding, the anti-interference performance of the (2,1,3) convolutional code using these two schemes in a mobile image communication system is studied and compared with the performance using traditional periodic interleaving scheme. The simulation results show that periodic interleaving scheme is not suitable for a convolutional code. The reliability of an image transmission system in a fast fading mobile channel can be improved greatly by adopting the (2,1,3) convolutional code combined with block interleaving scheme or bit interleaving scheme as the anti-interference measure.

In this paper, the performance comparison of serially concatenated Recursive systematic convolutional (RSC) code system with Non-systematic convolutional (NSC) code system is conduct. The two models of serially concatenated convolutional code is tested over Additive White Gaussian (AWGN) channel, Binary Phase-Shift Keying (BPSK) modulation and Viterbi decoder using MATLAB simulation. In first model of serially concatenated convolutional code uses Recursive systematic convolutional (RSC) as outer and inner encoder. In second model of serially concatenated convolutional code uses Non-systematic convolutional (NSC) as outer and inner encoder. The outer and inner encoders are concatenated with the help of interleaver. For decoding a non-iterative Viterbi decoding scheme is performed with two Viterbi decoder are concatenated by de-interleaver. The MATLAB simulation results shows that the performance of RSC-RSC concatenated code gives the better bit error rate (BER) than the NSC-NSC concatenated code.

Consideration is given to the bit error probability performance of rate 1/2 convolutional codes in conjunction with quaternary phase shift keying (QPSK) modulation and maximum-likelihood Viterbi decoding on fully interleaved Rician fading channels. Applying the generating function union bounding approach, an asymptotically tight analytic upper bound on the bit error probability performance is developed under the assumption of using the Viterbi decoder with perfect fading amplitude measurement. Bit error probability performance of constraint length K=3-7 codes with QPSK is numerically evaluated using the developed bound. Tightness of the bound is examined by means of computer simulation. The influence of perfect amplitude measurement on the performance of the Viterbi decoder is observed. A performance comparison with rate 1/2 codes with binary phase shift keying (BPSK) is provided. >

In this paper, we concern with designing and implementing a convolutional encoder and Viterbi decoder which are the essential block in digital communication systems using FPGA technology. Convolutional coding is a coding scheme used in communication systems including deep space communications and wireless communications. It provides an alternative approach to block codes for transmission over a noisy channel. The block codes can be applied only for the block of data. The convolutional coding has an advantage over the block codes in that it can be applied to a continuous data stream as well as to blocks of data.The motivation of this paper is to realize a Viterbi decoder having Constraint length 9 and code rate 1/2 by Xilinx 12.4i tools.

A new non-binary decoding method, which is called Yaletharatalhussein decoding algorithm, is designed and implemented for decoding non-binary convolutional codes which is based on the trellis diagram representing the convolutional encoder. Yaletharatalhussein decoding algorithm outperforms the Viterbi algorithm and other algorithms in its simplicity, very small computational complexity, decoding reliability for high states TCM codes that suitable for Fourth-Generation (4G), decreasing errors with increasing word length, and easy to implement with real-time applications. The proposed Yaletharatalhussein decoding algorithm deals with non-binary error control coding of the convolutional and TCM codes. Convolutional codes differ from block codes in that a block code takes a fixed message length and encodes it, whereas a convolutional code can encode a continuous stream of data, and a hard-decision decoding can easily be realized using the Yaletharatalhussein algorithm. The idea of non-binary codes has been extended for symbols defined over rings of integers, which outperform binary codes with only a small increase in decoding complexity. The simulation results show that the performance of the nonbinary TCM-based Yaletharatalhussein algorithm outperforms the binary and non-binary decoding methods.

In this study, a power-efficient very large-scale integration (VLSI) implementation for the convolutional code decoder is presented. Based on the state transparent convolutional code definition, the receiving codewords are classified into non-erroneous and erroneous segments separately. Different from the conventional Viterbi decoder (VD), the authors use a low-complexity decoder, denoted as bit reverse decoder, to recover the non-erroneous segments using reverse operation with a little power consumption and present the segment-based VD to decode the erroneous codeword segments. Then, the clock-gating technique is employed to switch between segment-based VD and bit reverse decoder for power saving. To further reduce the power consumption, the authors group registers into several segments in the survivor memory unit of the segment-based VD and also apply clock gating to each segment individually. According to the number of consecutive erroneous codeword segments, the corresponding numbers of register segments in the survivor memory unit are enabled and other register segments are clock-gated to reduce the switching activities. Besides, our design determines the start and terminal states of the survivor path to obtain correct results of erroneous segments without bit-error rate degradation. As compared with other decoders, our design requires less power without decreasing the decoding performance.

A new class of convolutional codes, called skew convolutional codes, that extends the class of classical fixed convolutional codes, is proposed. Skew convolutional codes can be represented as periodic time-varying convolutional codes but have a description as compact as fixed convolutional codes. Designs of generator and parity check matrices, encoders, and code trellises for skew convolutional codes and their duals are shown. For memoryless channels, one can apply Viterbi or BCJR decoding algorithms, or a dualized BCJR algorithm, to decode skew convolutional codes.

This paper addresses the implementation and performance of hybrid-ARQ error control on a coherent slowly fading Ricean channel. Using a convolutional code with soft-decision Viterbi decoding for error correction, there are two methods for realizing the simultaneous error detection capability which characterizes hybrid-ARQ error control: (1) a two code approach which pre-encodes the information based on a high rate CRC code and performs error detection on the output of the Viterbi decoder, (2) a single code approach which modifies the Viterbi decoder to reject packets with low reliability during the Viterbi decoding process. The resulting analysis shows that the two code method is more robust than single code method with the most significant performance advantages realized for Rayleigh fading. The two code approach provides acceptable error rate performance and offers a throughput characteristic which is not as sensitive to changes in the average SNR as the single code approach. Since the implementational complexity of the two methods is comparable, the two code method is the preferred implementation for hybrid-ARQ on flat fading channels.

In this paper, we present a framework for generic decoding of convolutional codes, which allows us to do cryptanalysis of code-based systems that use convolutional codes as public keys. We then apply this framework to information set decoding, study success probabilities and give tools to choose variables. Finally, we use this to attack two cryptosystems based on convolutional codes. In the case of Bolkema et al. (Variations of the McEliece cryptosystem. In: Algebraic geometry for coding theory and cryptography: IPAM, Los Angeles, CA, Feb 2016. Springer, Cham, pp 129-150, 2017. https://doi.org/10.1007/978-3-319-63931-4_5), our code recovered about 74% of errors in less than 10 h each, and in the case of Almeida et al. (Smaller keys for code-based cryptography: McEliece cryptosystems with convolutional encoders. CoRR abs/2104.06809, 2021. arXiv: https://arxiv.org/abs/2104.06809v1), we give experimental evidence that 80% of the errors can be recovered in times corresponding to about 70 bits of operational security, with some instances being significantly lower.

This paper studies the performance of ultra-wideband (UWB) radio communications systems employing phase shift keying (PSK) modulation and fully saturated power amplifiers through additive white Gaussian noise (AWGN) channel or Rayleigh fading channel. An impulse response method is provided to analyze the signal-to-noise ratio (SNR) degradation. Both convolutional code and turbo code are employed with the Viterbi decoding and the iterative decoding, respectively. The decoding algorithms are modified for the Rayleigh fading channel. Near optimal bit error rate (BER) performance is achieved when employing either convolutional code or turbo code. The simulation results match the derivation. Therefore, fully saturated power amplifiers can be employed in UWB PSK systems to significantly reduce radio cost, simplify radio circuit, and increase battery life for portable terminals.