Design of Cascaded Hybrid Interleaver for Fast Turbo Coding and Decoding
Turbo code in an attempt to realize a technique that approaches the theoretic limit utilizes a crucial component, interleaver, which converts burst errors caused by impulsive noise to simple errors. But the processing of data through the interleaver incur
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Abstract Turbo code in an attempt to realize a technique that approaches the theoretic limit utilizes a crucial component, interleaver, which converts burst errors caused by impulsive noise to simple errors. But the processing of data through the interleaver incurs time as well as memory. Both time and memory complexities are directly related to the total number of information bits. The time required for interleaver processing is so high because of which some applications omits the complete interleavers. But the consequent schemes suffer from high bit error rate. In this chapter a novel hybrid two stage interleaving scheme was proposed which reduces the time required for interleaving processing while maintaining the BER criteria up to the levels obtained with block or 3GPP interleavers. Keywords Interleaver
Turbo code Block interleaver 3GPP interleaver
1 Introduction The main function of a communication system is to transmit information from the source to the destination with sufficient reliability. In the last two decades, there has been an explosion of interest in the transmission of digital information mainly due to its low cost, simplicity, higher reliability and possibility of transmission of many services in digital forms [1]. M. Rajani Devi (&) JNTU Kakinada, East Gdavari District, Kakinada, AP, India e-mail: [email protected] K. Ramanjaneyulu PVP Siddhartha Institute of Technology, Kanuru, Krishna District, Vijayawada, AP, India e-mail: [email protected] B.T. Krishna JNTU, Vizianagaram, AP, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 S.C. Satapathy et al. (eds.), Computer Communication, Networking and Internet Security, Lecture Notes in Networks and Systems 5, DOI 10.1007/978-981-10-3226-4_53
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Theoretically, Shannon stated that the maximum rate of transmitted signal or capacity of a channel over Additive White Gaussian Noise (AWGN), with an arbitrarily low bit error rate depends on the Signal to Noise Ratio (SNR) and the bandwidth of the system (W), according to [2]. Instead of S/N, the channel capacity can be represented based on the signal to noise ratio per information bit (Eb/N0). Considering the relationship between SNR and Eb/N0, and the channel capacity (with value R). S Eb R ¼ X N No W C Eb R ¼ log2 1 þ : W No W In the case of an infinite channel bandwidth W ! 1; bound is defined by: Eb 1 ¼ 0:693 ¼ No log2 e
ð1Þ ð2Þ C W
! 0 the Shannon ð3Þ
In order to achieve this bound, i.e. NEbo ¼ 1:59 dB value, it would be necessary to use a code with such long length that encoding and decoding would be practically impossible. However, the most significant step in obtaining this target, was by Forney, who found that a long code length could be achieved by concatenation of two simple component codes with short lengths linked by an interleaver [3]. Conventionally, a turbo code is analyzed as a block code by using a block interleaver and terminating RSC encoders to a known state at the end of each data block. Codes with this
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