Optimizing Turbo Codes for Secret Key Generation in Vehicular Ad Hoc Networks

An efficient design of an interleaver is essential to achieve near Shannon capacity performance with turbo codes. The turbo code performance curve can change its slope in low bit error rate (BER) region, if the interleaver is not designed properly. In this paper the design of an interleaver that combines randomization and de-correlation property with regular permutation, and yet guaranties an enlarged minimum distance, is proposed. Our solution to design a deterministic interleaver outperforms the random and semi-random interleavers particularly for the turbo codes with short block length. Distance spectrum distribution and simulation results are presented and compared with well established S -random interleaver.

A new rate 1/2 turbo code with short memory 2 is developed in this paper. The proposed turbo code consists of two 4-state parallel concatenated non-punctured systematic rate-2/3 convolutional codes. Using a modified maximum a posteriori (MAP) decoding algorithm working on dual codes, its bit error rate (BER) performance is comparable to that of the classic 16-state turbo code at short block lengths, such as k=1024, while its decoding complexity is less than 1/8 that of the classic 16-state turbo codes; for information block length k=504, its BER performance is better than that of the (1008, 3, 6) LDPC codes with comparable decoding complexity. The dual code decoding algorithm is intrinsically partial parallel and a considerably higher throughput of the turbo decoder can be obtained compared with classic turbo codes consisting of punctured codes. The simulation results show that the proposed turbo code can be a competitive technique for short block length applications.

A novel method to combine encryption and channel coding in such a way as to get increased security without any additional complexity is presented in this paper. A secure communication system usually consists of an encryption block followed by the channel coder. The encryption block here is a Shrinking generator which is a Linear Feedback Shift Register (LFSR) based stream cipher system. The channel coding technique used is Turbo codes or Low Density Parity Check Codes (LDPC) that performs very well and provides results near Shannon's Limit. Controlled randomness using Pseudo Random Bit Sequence (PRBS) generator is incorporated during encoding of these codes to provide additional level of security in the system without any additional complexity. To achieve optimum decoding, soft decision decoding algorithms are used rather than hard decisions. Bit Error Rate (BER) performance of the proposed channel coders with keyed randomness is well analyzed for intended and un-intended users. Security of the system is analyzed by mounting Improved Linear Consistency Attack and the results show that a significant increase in security is achieved in a stream cipher based secure communication system without any additional increase in complexity by introducing security in channel coding.

We define super codes as the serial concatenation of punctured convolutional codes. Puncturing pattern and interleaver design techniques are presented so as to maximise the free distance of the code and thus the performance at very low bit error rates (BER). The performance of super codes is compared to turbo codes. For BERs around 10/sup -5/, turbo codes perform 0.1, 0.4 and 0.6 dB better than super codes for rates 3/4, 1/2 and 1/3, respectively. However, due to the use of serial concatenation, super codes have an interleaver gain of N/sup -2/, compared to only N/sup -1/ for turbo codes and interleaver size N. Thus, super codes are expected to perform significantly better at BERs around 10/sup -10/.

For the Bennett-Brassard 1984 (BB84) quantum key distribution, longer distance and higher key generation rate is shown with a heralded single photon source (HSPS). In this paper, the nonorthogonal encoding protocol SARG04 based on one vacuum and two weak decoy states with HSPS is presented. According to the public announcement of Alice's detection events, the overall gain of Bob's detector and quantum bit error rate (QBER) can be divided into two groups, triggered components and nontriggered components. We present a new protocol that use both triggered and nontriggered components to estimate the fraction and QBER of single-photon and two-photon pulses, and then deduce the final secure key generation rate. The final key generation rate over transmission distance is simulated, which shows that we can obtain a higher key rate than that of the existing methods.

Internet-of-Things (IoT) networks generally contain resource-constrained devices that require an energy-efficient key generation procedure to producing secure keys at a faster rate. The physical characteristics of the wireless channel can be exploited to secure communication within IoT networks. In particular, secret keys can be generated by leveraging on the randomness of the wireless physical channel between two communicating parties. The conventional mechanism of generating keys at the physical layer, i.e., using channel probing, quantization, information reconciliation, and privacy amplification, may not be preferable for IoT devices. In addition, in some cases IoT devices may be deployed in static environments, wherein the channel coherence time is too high to generate keys at a faster rate and with the desired randomness. This study proposes a mapping table-based key distribution scheme for IoT environments, wherein multiple characteristics of the random channel are combined to improve not only the key generation rate (KGR) but also the key agreement rate (KAR) and bit error rate (BER). In the proposed scheme, both the channel magnitude and the phase are exploited in the key generation process. The proposed scheme is immune to channel estimation errors while providing sufficient randomness in the static environment. Additionally, the scheme is thoroughly investigated for different scenarios including the case of a smarter eavesdropper, which attempts to estimate the channel between the legitimate nodes. This case verifies the robustness of the proposed scheme in different settings and attack models.

With heralded pair coherent states (HPCS), orbital angular momentum (OAM) states and pulse position modulation (PPM) technology, a decoy-state measurement-device-independent quantum key distribution (MDI-QKD) protocol is proposed. OAM states and PPM technology are used to realize the coding of the signal states in the HPCS light source. The use of HPCS light source, OAM coding and PPM coding cannot only reduce the error rate but also improve the key generation rate and communication distance. The new MDI-QKD protocol also employs three-intensity decoy states to avoid the attacks against the light source. By calculating the error rate and key generation rate, the performance of the MDI-QKD protocol is analyzed. Numerical simulation shows that the protocol has very low error rate and very high key generation rate. Moreover, the maximum communication distance can reach 455 km.

Key generation rate and bit disagreement ratio are two main indicators to evaluate the performance of physical layer key generation (PLKG). This work explores the key generation performance in reconfigurable intelligent surface (RIS)-assisted PLKG, where a concrete scheme of key generation is proposed. Specifically, we first deduce the key generation rate expression based on estimation theory in RIS-assisted PLKG. Then we optimize the RIS reflecting coefficients with instantaneous channel state information to maximize the key generation rate. Finally, aiming at minimizing transmit power while guaranteeing key generation rate target, we formulate a power minimization problem in RIS-assisted PLKG. An alternating optimization algorithm is applied to solve the non-convex mixed-integer nonlinear programming. Simulation results demonstrate that the key generation rate of the proposed scheme is up to 197.5% higher than the existing relay-assisted scheme, and we successfully reduce the required transmit power by at least 6.6 dBm than without power minimization scheme.

차세대 무선통신에서는 현재 서비스 되고 있는 성능보다 높은 BER(Bit Error Rate)의 성능을 요구한다. 기존의 DVB-RCS(Digital Video Broadcasting - Return Channel via Satellite)에서 사용중인 이진 터보 코드(Double binary Turbo code)는 높은 SNR(에서 오류마루 현상이 발생하여 차세대 무선통신에서 사용하기가 어려움이 있다. 따라서 본 논문에서는 DVB-RCS NG에 적합한 부호화 방식으로 3D-터보 코드(Tthird-dimension Turbo code)의 부복호화기의 구조를 분석하고 성능분석 하였다. 3D-터보 코드는 기존의 DVB-RCS 방식에 rate-1인 post-encoder를 첨가시켜 오류마루 현상을 보완한 부호화기이다. 3D-터보 코드는 post-encoder의 형태, 인터리빙 기법, <TEX>${\lambda}$</TEX>값의 변화에 따라 성능이 달라지므로 본 논문에서는 각 파라메타에 대한 최적의 값을 제시하였다. 전체적으로 3D-터보 코드가 기존의 DVB-RCS 터보 코드에 비해 성능이 우수하고 기존의 문제점인 오류마루 현상을 해결할 수 있음을 알 수 있다. The next generation wireless communication systems are required high BER performance better than present performance. Double binary Turbo code have error floor at high SNR, so it cannot be used in next generation wireless communication system. Therefore, many methods are proposed for overcome error floor at DVB-RCS NG(next generation). In this paper, we analysis structure of third-dimension Turbo code(3D-turbo code). 3D-Turbo code overcomes error flow by additive post-encoder in conventional DVB-RCS Turbo code. Performance of 3D-Turbo code is changed by post-encoder form, interleaving method, value of <TEX>${\lambda}$</TEX>. So we are simulated by those parameter and proposed optimal form. By a result, performance of 3D-Turbo is better than conventional DVB-RCS Turbo code and it overcome error floor of conventional DVB-RCS Turbo code.

Cooperation is an effective technique to increase the diversity in wireless relay networks and hence improve the Bit Error Rate (BER). In this paper, a scheme combining turbo coding and cooperative relay techniques, comprising one source, one destination and a single relay is proposed and studied. The aim of this study is to investigate the bit error rate (BER) performance in cooperative turbo coded systems equipped with an omni-directional antenna element at the transmission and the reception in the presence of channel estimation errors. Herein, the Amplify-and-Forward (AF) cooperation protocol is adopted at the relay level. Furthermore, a single hop scenario is considered, and the imperfect channel state information (CSI) is assumed to be present at the source-destination link. Two turbo codes, are generated at the source using the same polynomial, with overall rates of 1/2 and 1/3, respectively, the 1/2-rated one being generated from the latter using puncturing. Before iterative decoding, the destination performs a maximum ratio combing (MRC) of the signals emanating from the source and the relay transmitters. According to the authors 'knowledge, the investigation of the effect of channel estimation errors on the performance of such systems has not yet been reported.

Frequency offset (FO) introduces severe inter-symbol and inter-carrier interferences which will degrade the performances of orthogonal frequency division multiplexing (OFDM) system more adversely. To reduce the effect of CFO, an estimation algorithm has been proposed in this work which uses a turbo coding at the precoding section and Space time block coding techniques (alamouti code) for transmitting data. The turbo codes solve dilemma of structure and randomness through concatenation and interleaving and it will reduce bit error rate (BER) by error detection and error correction process. A fading channel has been modeled for evaluating the performance of the algorithm. Maximum likelihood (ML) estimation is used for the estimation that does take conditional probability into account. The offset estimation in OFDM is done by best linear unbiased estimator (BLUE) principle yet it has disadvantages that it is already sub optimal in nature and it is applicable only for linear observation models. So, ML technique is an alternative estimation criterion that can use as starting point of most of the statistical estimation and for nonlinear observations. The proposed system has improved BER while other methods supports BER of 25-30 dB and the proposed system shows improvement in spectral efficiency as well as the Power spectral density.

In this chapter, a novel algorithm named as modified ant lion optimizer (MALO) algorithm has been suggested for the improvement of convergence behavior of the existing ALO algorithm. Moreover, a new form of turbo code (TC) termed as 4D-TC has also been projected for the enhancement of the minimum Hamming distance of the existing TCs. Thereafter, the MALO algorithm has been judiciously used for the design of power efficient 4D-TC. From the simulated outcomes, it is obvious that the high-grade act of MALO algorithm is pretty remarkable than the existing ALO as well as other optimization procedures like particle swarm optimization, Cuckoo search and Harmony search in the matter of exactness and confluence standpoint. Additionally, it has been witnessed that the projected modification on ALO algorithm provides the best optimum value close to theoretical limit by adopting fast exploration and exploitation process over the other algorithms. At the same time, it has also been established that the projected 4D-TC offers substantial improvement in BER act over the others like parallel concatenated convolution turbo code (PCCTC), serially concatenated convolution turbo code (SCCTC), and 3D-TC. The supremacy of MALO has been observed for eight states as well as 16 states 4D-TCs over the other variance like PCCTC, SCCTC, 3D-TC and proposed 4D-TC by means of bit error rate (BER) performance by allocating the optimum power to the systematic and parity bits. Analogous enhancements in BER act have been detected with puncturing as well.

The physical characteristics of the wireless channel can be exploited to secure communication within Internet-of-Things (IoT) networks. Several techniques have been proposed in the literature; however, the feasibility of such techniques in IoT environments remains unclear. In some cases IoT devices may be deployed in static environments wherein the channel coherence time is too high to generate keys at a faster rate and with the desired randomness. On the other hand, in some cases IoT devices are deployed in dynamic environments wherein the channel properties changes very fast over the time. Key generation schemes proposed for one environment are not directly applicable to the other. While low key generation rate (KGR) is an issue for static environments, higher values of bit error rate (BER) becomes a bottleneck in dynamic environments. This paper proposes a mapping-table based key distribution scheme for IoT networks deployed in both static and dynamic environments. In the proposed scheme, the channel magnitude is exploited in the key generation process. The proposed scheme is immune to channel estimation errors, while providing sufficient randomness in the static environment.

In this paper, the performance evaluation of an asymmetric turbo code for different codec parameters have been done. The asymmetric turbo codes performances are compared with symmetric counter part of the turbo code. With proper selection of weight configuration, the turbo code can show better results in both water fall region as well as error floor region simultaneously. So, in some cases asymmetric turbo code's performance is more nearer to Shannon limit than symmetric one. This paper includes the effect of different codec parameters (like no. of iteration, frame size, code-rate, and generator polynomial Structure & constraint length etc) on asymmetric turbo code and also explains its performance in comparison with symmetric turbo code. Although, the asymmetric turbo code of all combinations don't show better performance always. Here, we have evaluated the bit error rate (BER) performance using sub-optimal Log-MAP (Logarithmic Maximum-A-Posteriori) decoding algorithm under Additive White Noise (AWGN) channel. The simulation model was developed for AWGN case using MATLAB.

The fifth-generation (5G) wireless communication system promises to revolutionize global connectivity by offering ultra-high-speed data transfer, massive device connectivity, and low latency. However, achieving these objectives demands efficient spectrum allocation and error-correcting mechanisms. The scarcity of radio spectrum and interference management are key challenges, necessitating optimized solutions for spectrum allocation. Additionally, reliable communication over noisy channels requires robust error-correcting codes. Optimized turbo codes, known for their iterative decoding capabilities, have emerged as a viable solution to enhance error resilience and throughput in 5G networks. This research proposes an integrated approach to optimize spectrum allocation and turbo code performance. The spectrum allocation employs a dynamic multi-objective optimization model based on machine learning algorithms, prioritizing fairness, quality of service (QoS), and interference minimization. Simultaneously, an improved turbo coding algorithm utilizing adaptive puncturing and interleaving strategies enhances data integrity. Simulations conducted in a heterogeneous 5G environment demonstrate significant performance improvements. The optimized turbo codes achieve a Bit Error Rate (BER) of 10-5 at a Signal-to-Noise Ratio (SNR) of 2.5 dB, outperforming conventional turbo codes by 40%. The proposed spectrum allocation strategy enhances spectral efficiency by 25%, ensuring equitable resource distribution and improved QoS. This integrated framework highlights the potential for scalable and efficient 5G systems, addressing the dual challenges of spectrum scarcity and error correction.