Performance Investigation of MIMO Based CO-OFDM FSO Communication Link for BPSK, QPSK and 16-QAM under the Influence of Reed Solomon Codes

The MIMO based CO-OFDM FSO communication system is emerging as a promising approach to meet the future bandwidth requirements for seamless communication. The atmosphere being the propagation medium is a major hindrance in wide-scale acceptability of FSO technology. For seamless and error-free transmission and reception of data, a novel concept of MIMO integrated with RS code is proposed in this paper. The system performance of an RS 64 (RS (255,127)) coded MIMO-based CO-OFDM FSO communication link was investigated using BPSK, QPSK and 16-QAM under the combined effects of geometric losses, path losses and atmospheric attenuations at a hitherto un-investigated data rate of 40 Gbps and a link distance of 5 km. The modified gamma-gamma distribution was used for modeling a moderately turbulent channel. With link length varying over a range of 1 to 5 km, error correction was maximum in 16-QAM as compared to BPSK and QPSK, with 150 to 167 corrected errors. In terms of PAPR, PSK was more apt than QAM, but with a compromise in BER. The geometric losses were reduced with link length due to an increase in error correction capability for all three modulation cases, with the least losses occurring in 16-QAM. At the target bit error rate (BER), the signal to noise ratio (SNR) required for BPSK and QPSK was higher by 3.98 dB and 6.14 dB compared to 16-QAM.

Blind Recognition of Parameters of Reed Solomon Code from Intercepted Erroneous Codewords

Error correcting codes are designed for reliable transmission of digital information over a noisy channel. Several papers have been published on blind identification of binary FEC codes but papers reported on the identification of non-binary error correcting codes are less. Due to its strong error correction capability, RS (Reed-Solomon) code is being used widely. So technique for blind recognition of RS code is required to analyse intercepted signal as well as for intelligent communication. This paper presents a technique for extraction of parameters of Reed-Solomon code from intercepted demodulated bitstream. The proposed algorithm is very simple and hence it is very practical for hardware implementation. Our approach has been verified using MATLAB simulation.

Error correction by Reed–Solomon codes using its automorphisms

The article explores the syndrome invariants of АГ-group of automorphisms of Reed–Solomon codes (RS-codes) that are a joint group of affine and cyclic permutations. The found real invariants are a set of norms of N Г-orbits that make up one or another АГ-orbit. The norms of Г-orbits are vectors with 2 1 Cδ− coordinates from the Galois field, that are determined by all kinds of pairs of components of the error syndromes. In this form, the invariants of the АГ-orbits were cumbersome and difficult to use. Therefore, their replacement by conditional partial invariants is proposed. These quasi-invariants are called norm-projections. Norm-projection uniquely identifies its АГ-orbit and therefore serves as an adequate way for formulating the error correction method by RS-codes based on АГ-orbits. The power of the АГ-orbits is estimated by the value of N2, equal to the square of the length of the RS-code. The search for error vectors in transmitted messages by a new method is reduced to parsing the АГ‑orbits, but actually their norm-projections, with the subsequent search for these errors within a particular АГ-orbit. Therefore, the proposed method works almost N2 times faster than traditional syndrome methods, operating on the basic of the “syndrome – error” principle, that boils down to parsing the entire set of error vectors until a specific vector is found.

System Design for Opportunistic Spectrum Access Using Statistical Decision-Making and Coded-MAC

Different mechanisms have been proposed to solve opportunistic spectrum access (OSA). In order to address spectrum management efficiently, these mechanisms can be divided into four main functionalities, spectrum sensing, decision-making, sharing, and mobility. These functionalities depend on the interpretation and adaptation of different parameters, for example, sensing and data interpretation for adaptive modulation, power adjustments, and changes regarding the range of frequency operation. For the decision-making function, a novel approach is proposed in which coding information is added to the establishment of the communication process thus assisting the medium access control (MAC). The presence of cognitive radio devices in the network coverage range can be controlled or coordinated by using specific redundancy codes. Hence, Reed Solomon (RS) code is used in this paper as part of the handshaking process to provide error correction. In addition, a redundancy strategy based on Rabin’s information dispersal algorithm (IDA) is presented to provide fault tolerance to the communication between cognitive radio devices. In this case, the information is divided into fragments dynamically, and each fragment is coded by an RS code and reassigned to a subset of recipients using alternate paths. This work shows how to optimize spectrum access based on IDA and RS codes to diversify channel occupation without losing significant information with several frequency hops presented in cognitive radio communications. The validations were executed in a discrete event simulator developed in Python. The proposed system for OSA was found to perform better than other approaches using pilot sequences. Our proposal, therefore, provides fault tolerance, to diversify channel occupation, and helps identify the presence of primary and secondary users when a common control channel (CCC) is implemented by the optimization of the spectrum use.

GFDM Based Error Correcting Codes in Underwater Acoustic Channel

In this paper underwater acoustic communication system based on Coded GFDM (CGFDM) is simulated and the performances are analyzed using different error-correcting codes. And also the parameter selection principle of error-correcting code is evaluated. To build practical and high performance CGFDM system the error-correcting codes from low to relatively high computational complexity, such as, convolutional code, RS code, serial concatenated code of RS code plus convo1utional code and turbo code is evaluated. The parameters of code rate, code length, generation polynomial, interleaving and interleaving matrix length are all considered and analyzed elaborately. Finally, the simulating experiments proved that there are some relative1y low complexities systems based on serial concatenated codes of RS code plus convolutional code that are able to gain better performance as the systems based on turbo code.

Forward Error Correction For Gigabit Automotive Ethernet using RS(450,406) Encoder

Error correction and detection during data transmission is a major issue. For resolving this, many error correction techniques are available. The Reed-Solomon coding is the most powerful forward error correction technique used in Gigabit Automotive Ethernet to compact channel noise during data transmission. The car becomes more smarter day by day and more new advanced electronics is being used in-vehicle. Gigabit Automotive Ethernet(1000BASE-T1) provide fast bandwidth for many kinds of applications and connect different functional parts in the car. The Reed Solomon(RS) coding is the powerful forward error correction(FEC) technique used in 1000BASE-T1 Automotive Ethernet. RS(450,406) coding is also known as shortened Reed Solomon codes. The Reed Solomon(RS) codes are generally used in communication system due to its ability of correcting both random and burst errors. Reed Solomon codes are no-binary systematic linear block codes. RS coding is widely used in high speed communication system. This RS code is implemented using Galois field(GF). The Automotive Ethernet is encoded using RS(450,406) codes through GF(512) for FEC. This RS codes can corrects the error up to t=22 symbol, while other encoding techniques corrects the error in t bits. In this paper we implemented the RS(Reed Solomon) code in Cadence ncsim Verilog software and used Cadence Simvision for showing timing diagrams. This RS code uses 9-bit based shortened (450,406) code.