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Coding and Modulation for Free-Space Optical Communications
Published in Hamid Hemmati, Near-Earth Laser Communications, 2020
Turbo codes [30] achieved a breakthrough in code performance by combining a pair of CCs in parallel to form one large code. In a turbo code, a block of data is encoded by one CC. The same data is interleaved, and encoded by a second CC. A maximum likelihood decoder of the subsequent, typically long, block code would be prohibitively complex to implement. A key insight of turbo codes was to use a suboptimal decoder, decoding each constituent code independently, and passing information between them in an iterative manner. This decoding algorithm proves to have excellent performance in practice, achieving near capacity performance. Conventional turbo codes (parallel concatenated codes as described above) were applied to the PPM channel in Ref. [31–33], demonstrating large gains over RSPPM.
Codec Design
Published in Rajeshree Raut, Ranjit Sawant, Shriraghavan Madbushi, Cognitive Radio, 2020
Rajeshree Raut, Ranjit Sawant, Shriraghavan Madbushi
A convolutional encoder converts the entire input stream into length n codewords independent of the length k. The development of convolutional codes is based mostly on physical construction techniques [2]. The evaluation and the nature of the design of convolutional codes depend less on an algebraic manipulation and more on construction of the encoder. A codec design has been proposed wherein a turbo encoder is used in concatenation with an RS encoder. Turbo coding represents a new and very powerful error control technique, which has started to have a significant impact in the late 1990s, allowing communication very close to the channel capacity. They were introduced in 1993 by Berrou, Glavieux, and Thitimajshima [3]. The powerful error correction capability of turbo codes was recognized and accepted for almost all types of channels, leading to increased data rates and improved quality of service. The introduction of turbo codes made signaling possible at power efficiencies close to the Shannon’s limit of 1.59 dB. In principle, turbo code is the parallel concatenation of two or more systematic codes. Turbo decoder uses iterative decoding. The turbo code decoder is based on a modified Viterbi algorithm that incorporates reliability values to improve decoding performance. The turbo decoder consists of M elementary decoders, one for each encoder in turbo encoding part. Each elementary decoder uses the soft decision Viterbi decoding to produce a soft decision for each received bit.
Communications Applications
Published in David R. Martinez, Robert A. Bond, Vai M. Michael, High Performance Embedded Computing Handbook, 2018
Joel I. Goodman, Thomas G. Macdonald
There are many forms of coding such as linear block/cyclic codes, convolutional codes, lowdensity parity check (LDPC) codes, and turbo codes (Sklar and Harris 2004). These different types of codes each have strengths and weaknesses. Many of the most advanced codes, such as turbo codes, are very close to achieving the theoretical lower limit on energy required for error-free communication (Berrou and Glavieux 1996). Turbo codes are widely used today both in commercial systems (e.g., cell phones) and for military applications. However, because the more advanced FEC codes typically require more processing, they may not be good choices for very-high-rate systems or systems that are severely limited in processing power.
Performance Analysis of Reliability-Based Decoding Algorithm for Short Block Length Turbo Codes
Published in IETE Journal of Research, 2022
P. Salija, B. Yamuna, T. R. Padmanabhan, Deepak Mishra
The demand for communication with short data blocks is increasing in recent years. Real-time communication and low latency applications require communication with short block length codewords. Strong channel codes are required to ensure reliable transmission over dynamic channel conditions. The demand for communication with short block Turbo codes is increasing in applications like mobile communication, wireless sensor networks, and satellite communication. In this paper, the performance of the novel reliability-based algorithm has been analyzed for 3GPP LTE, and CCSDS Turbo codes. Simulation results show that the algorithm outperforms the conventional iterative Turbo decoder in terms of BER performance. The time complexity of the performance-enhanced reliability-based Turbo decoder shows a clear advantage as SNR increases. The performance flattening at high SNR region is completely eliminated with the proposed decoding algorithm. This is a clear advantage for applications requiring communications with short block length Turbo codes. The algorithm is an attractive solution to achieve reliable and timely transmission of short block length Turbo codes in mobile and satellite communication applications. The proposed algorithm has a coding gain of 2.45 dB at a BER of 10−3 over AWGN channel with BPSK modulation for a code rate of . The algorithm has a channel adaptive complexity and has shown nearly 82% reduction in the decoding time complexity for the rate Turbo code at 3 dB SNR. The performance analysis of the level based Turbo decoding algorithm gives an insight into an alternate decoding approach for Turbo codes.
Overview of the challenges and solutions for 5G channel coding schemes
Published in Journal of Information and Telecommunication, 2021
Madhavsingh Indoonundon, Tulsi Pawan Fowdur
Even though Turbo codes have good error performances for large message blocks, their high complexity prevents them from being good contenders for 5G applications. By properly reducing their complexity, they can become more suitable candidates for eMBB services than the currently selected LDPC and Polar codes. However, only a few studies are going in this direction. Additionally, once a lower complexity Turbo code is identified, hybrids of Turbo codes such as Turbo-LDPC and Turbo-Polar codes can be designed and assessed for suitability with 5G applications.
Efficient coding techniques for flip-OFDM in IM/DD systems
Published in International Journal of Electronics Letters, 2019
Muhammed Abd El-Aziz Eltoukhi, Mohammed Abd-Elnaby, Sami A. El-Dolil, Fathi E. Abd El-Samie
Turbo codes, first introduced in 1993, are high-performance Forward Error Correction (FEC) codes, and they have been used in a variety of modern wireless applications including satellite and fixed wireless systems. Turbo codes use an iterative decoding algorithm that closely approaches the channel capacity, but this increases the computational complexity and latency.