Performance Comparison of Turbo Decoding Algorithms

Lecture Notes in Electrical Engineering, 2009

Iterative decoder implementation for turbo codes is an demanding assignment. Several algorithms have been projected to facilitate the implementation of iterative decoder for turbo codes. This paper examines the implementation of an iterative decoder for turbo codes using the MAX−LOG−MAP algorithm and Fully parallel turbo decoding algorithm (FPTD). Despite the fact that the MAX-LOG-MAP practices turbo encoded bits in a serial forward-backward style, the proposed algorithm functions in a fully-parallel behaviour, processing all bits in both components of the turbo code at the same time. The FPTD algorithm is attuned with all turbo codes, including those of the LTE and WiMAX standards. BER performance among these two algorithms is envisaged.

Turbo codes are the best coding scheme for error correction in high-speed wireless systems because they achieve the highest coding gain. However, the implementation of various Turbo Decoders suffers from a large delay and high power consumption. For this reason, they are not suitable for many applications like mobile communication systems. In this paper, a comparative study has been made and various decoding algorithm used in SISO Turbo Decoders have been analyzed viz. MAP, Log-MAP, Max-Log-MAP and SOVA, to overcome this drawback. It presents the discussion of complexity and performance trade-offs of SISO Turbo decoders

2013

Use of turbo codes is more popular in most of the wireless applications, because of its greater Error control ability. The BER performance reaches to the Shannon’s channel capacity limit. Turbo code implementation using SISO decoders with iterative MAP decoding algorithms introduces large time delay to recover the transmitted information bits. This results in increasing Wi-Max system complexity and storage requirement (M emory size). In this paper, the efforts have been made to propose the methods for effective termination of iterations to make the decoder efficient, in terms of reduction in the time delay and the requirement of memory size while maintaining the BER performance. Authors have propose various termination techniques which help in reducing the complexity as compare to conventional MAP decoding algorithm for same BER performance.

In order to have reliable communication, channel coding is often employed. Turbo code as a powerful coding technique has been widely studied and used in communication systems. Turbo coding is an advanced forward error c o r r e c t i o n a l g o r i t h m . U l t i m a t e Performance that approaches the Shannon limit requires a new approach using iteratively run soft in/soft out (SISO) decoders called turbo decoders. However, the implementation of various Turbo Decoders suffers from a large delay and high power consumption. For this reason, they are not suitable for many applications like mobile communication systems. In this paper, a comparative study has been made and various decoding algorithm used in SISO Turbo Decoders have been analyzed viz. MAP, Log-MAP, Max-Log-MAP and SOVA, to overcome this drawback. This paper examines the principles of turbo coding and decoding algorithms and compare their BER performance.

International Journal of Computer Applications, 2012

Turbo codes are family of forward error correcting codes, whose performance is near Shannon limit. Turbo decoding is based on the maximum a-posterior algorithm (MAP) algorithm. In this paper, the problem of turbo decoding in ISI channel is studied. A Super-trellis structure method has been presented and modified turbo decoding is suggested. Two methods have been suggested for turbo decoding in ISI channel. In the first method, we take all possible combinations of output of encoder-2 and in method-2, output of each encoder is passed through channel filter independently. Method-2 performs better than method-1 but requires higher bandwidth. The improvement in performance is demonstrated through simulations.

Journal of Advanced College of Engineering and Management, 2018

This paper presents a Thesis which consists of a study of turbo codes as an error-control Code and the software implementation of two different decoders, namely the Maximum a Posteriori (MAP), and soft-Output Viterbi Algorithm (SOVA) decoders. Turbo codes were introduced in 1993 by berrouet at [2] and are perhaps the most exciting and potentially important development in coding theory in recent years. They achieve near-Shannon-Limit error correction performance with relatively simple component codes and large interleavers. They can be constructed by concatenating at least two component codes in a parallel fashion, separated by an interleaver. The convolutional codes can achieve very good results. In order of a concatenated scheme such as a turbo codes to work properly, the decoding algorithm must affect an exchange of soft information between component decoders. The concept behind turbo decoding is to pass soft information from the output of one decoder to the input of the succeeding one, and to iterate this process several times to produce better decisions. Turbo codes are still in the process of standardization but future applications will include mobile communication systems, deep space communications, telemetry and multimedia. Finally, we will compare these two algorithms which have less complexity and which can produce better performance.

Keywords__ Block interleaved pipelining, convolutional Turbo codes,Max log maximum a posteriori,Single Binary and Double Binary

IEEE Transactions on Instrumentation and Measurement, 2000

This paper proposes an improved Max-Logmaximum a posteriori (MAP) algorithm for turbo decoding and turbo equalization. The proposed algorithm utilizes the MacLaurin Series to expand the logarithmic term in the Jacobian logarithmic function of the Log-MAP algorithm. In terms of complexity, the proposed algorithm can easily be implemented by means of adders and comparators as this is the case for the Max-Log-MAP algorithm. In addition, simulation results show that the proposed algorithm performs very closely to the Log-MAP algorithm for both turbo decoding over additive-white-Gaussian-noise channels and turbo equalization over frequencyselective channels. Further, it is shown than even in a high-loss intersymbol-interference channel, the proposed algorithm preserves its performance close to that of the Log-Map algorithm, while there is a wide gap between the performance of the Log-MAP and Max-Log-MAP turbo equalizers.

Communications on Applied Electronics, 2016

Turbo decoding for 3GPP-LTE wireless communication standard is most challenging task to reduce computational complexity. The complexity of Turbo decoder is much higher than the complexity of Turbo encoder. Turbo decoder complexity depends on decoding algorithm. Less complexity in decoding gives degraded performance. Turbo decoder performance also depends on the number of iterations used during decoding. This paper describes different types of iterative Turbo decoding algorithm. The correction factor, how it deviates in different algorithms is discussed. BER analysis is done for different Turbo decoding algorithms. The effect of number of iterations for Max-Log-MAP decoding is shown using MATLAB simulation.