HSSEC strategy for decode-and-forward-relaying systems over Nakagami-m fading channels

Distributed switched diversity combining has drawn significant attention in the recent past due to its low-complexity nature in terms of channel state information requirement at the receiving end to achieve full diversity order. In this study, the authors propose a hybrid selection and switch-and-examine combining (HSSEC) scheme, which is a combination of selection combining and SEC schemes, for a multi-relay decode-and-forward system to improve the performance of distributed switched diversity combining schemes proposed in the literature. Furthermore, the performance of HSSEC scheme is investigated over non-identical Nakagami-m fading channels. Average end-to-end symbol error probability (SEP) expression is derived for M-ary phase-shift keying signalling, and in addition asymptotic SEP expression is also derived to analyse diversity order. From the derived asymptotic expression, it is inferred that the HSSEC scheme attains full diversity order over Nakagami-m fading channels, except for the case when threshold signal-to-noise ratio (SNR) is very much lesser than the average SNR. Furthermore, exact outage probability expression is derived for the HSSEC scheme. Finally, in the numerical results, the outage and SEP performances are compared with other schemes proposed in the literature.Accepted versio

Joint Recognition of Error Correcting Codes and Interleaver Parameters in a Robust Environment

To improve the error performance of digital storage and communication systems, forward error correcting (FEC) codes and interleaver play a significant role by counteracting random and burst errors, respectively. In most of the applications, accurate information about the type of FEC codes, coding and interleaving parameters are known at the receiver in order to successfully decode and de-interleave the message bits, respectively. However, in certain applications such as spectrum surveillance, adaptive modulation and coding (AMC)-based communication systems, cognitive radio, etc., all the coding and interleaving parameters need not be known at the receiver and blind/semiblind recognition of the same is mandatory. Therefore, in this paper, innovative algorithms for automatic recognition of type of FEC codes along with the parameter estimation of helical scan interleaver are proposed considering both erroneous and non-erroneous scenarios without any prior knowledge about the encoding scheme used in the transmitter. Note that the proposed algorithms will classify among block coded, convolutional coded, and uncoded data streams.Accepted versio

Performance of hybrid selection and switch-and-stay combining with decode-and-forward relaying

In this letter, an uncoded cooperative diversity system with a source, two decode-and-forward (DF) relays, and a destination (D) is considered. We propose a hybrid selection and switch-and-stay combining (HSSSC) scheme at D. Furthermore, we also derive the exact symbol error probability (SEP) of this scheme for DF relaying over slow and flat Rayleigh fading channels considering M-ary phase-shift keying (MPSK) signaling using paired error approach. Numerical results reveal that full diversity order is achieved in the case of HSSSC scheme and improvement in the SEP performance is observed when compared to the distributed selection combining (SC), distributed scaled selection combining, and distributed switch-and-stay combining schemes proposed in the literature. In addition, the HSSSC scheme requires less channel state information (CSI) at D compared to the distributed full CSI SC scheme proposed in the literature

Blind parameter estimation of turbo convolutional codes : noisy and non-synchronized scenario

Blind estimation of forward error correction code parameters at the receiver plays a significant role in non-cooperative communication, adaptive modulation and coding systems, and reconfigurable receiver systems. Turbo convolutional codes, a parallel concatenation of multiple convolutional codes, are used in digital communication and storage systems to achieve low bit error rate. The present paper proposes innovative algorithms for the blind estimation of code parameters and reconstruction of turbo convolutional encoder over noisy scenario. The turbo convolutional code is designed using two component codes along with an interleaver. Recursive systematic convolutional codes are used as component codes. Any imperfection in synchronization of received data for the proposed code parameter estimation algorithm is compensated through a bit position adjustment parameter. The performance of the proposed algorithms in terms of parameter estimation accuracy is investigated for different modulation order, code rate, and constraint length values. It is observed that the performance improves with decrease in modulation order and constraint length values.Accepted versio

Classification of error correcting codes and estimation of interleaver parameters in a noisy transmission environment

Channel encoder, which includes a forward error correcting (FEC) code followed by an interleaver, plays a vital role in improving the error performance of digital storage and communication systems. In most of the applications, the FEC code and interleaver parameters are known at the receiver to decode and de-interleave the information bits, respectively. But the blind/semi-blind estimation of code and interleaver parameters at the receiver will provide additional advantages in applications such as adaptive modulation and coding, cognitive radio, non-cooperative systems, etc. The algorithms for the blind estimation of code parameters at the receiver had previously been proposed and investigated for known FEC codes. In this paper, we propose algorithms for the joint recognition of the type of FEC codes and interleaver parameters without knowing any information about the channel encoder. The proposed algorithm classify the incoming data symbols among block coded, convolutional coded, and uncoded symbols. Further, we suggest analytical and histogram approaches for setting the threshold value to perform code classification and parameter estimation. It is observed from the simulation results that the code classification and interleaver parameter estimation are performed successfully over erroneous channel conditions. The proposed histogram approach is more robust against the analytical approach for noisy transmission environment and system latency is one of the important challenges for the histogram approach to achieve better performance.Accepted versio

Code parameter estimation from noisy data : TPC

A novel algorithm has been proposed for the blind estimation of two-dimensional turbo product code (TPC) parameters over noisy channel conditions. The performance of the algorithm is investigated for different code dimension values.Published versio

Performance analysis of HAPS-based relaying for hybrid FSO/RF downlink satellite communication

Free space optics (FSO) communication has garnered significant importance to provide gigabit capacity links owing to its unique features. However, its performance is limited by the adverse effects of transmission medium such as atmospheric turbulence induced fading, wind, etc. Therefore, it is wise to backup with reliable radio frequency (RF) links to improve the performance of FSO communication. The fusion of FSO and RF technologies is a suitable candidate for future satellite communication (SATCOM) systems. In this context, the present paper proposes a novel system model for High-Altitude Pseudo-Satellite (HAPS)-based relaying for downlink scenario utilizing both FSO and RF links. The performance of the proposed hybrid FSO/RF SATCOM system is investigated through average and asymptotic symbol error probability (SEP) analyses. Further, the obtained closed-form expressions for average SEP are validated using Monte-Carlo simulation results.Ministry of Education (MOE)Accepted versionThis work was supported by the Start-up Research Grant (SRG) of Science and Engineering Research Board (SERB), Department of Science and Technology, Govt. of India (Project no. SRG/2019/000464) and Singapore Ministry of Education Academic Research Fund Tier 1 grants

On the Error and Outage Performance of Decode-and-Forward Cooperative Selection Diversity System With Correlated Links

A cooperative diversity system improves the communication reliability and throughput in a multipath fading environment with the help of relay nodes. We consider a cooperative diversity system with a source (S), a decode-and-forward relay (R), and a selection-combining-enabled destination (D). In this paper, we derive the exact end-to-end symbol error probability (SEP) for -ary phase-shift keying (MPSK) signaling using a paired error approach and differential binary phase-shift keying (DBPSK) signaling over correlated, nonidentical, slow, and flat Nakagami- fading channels by assuming the correlation between SD–RD, SR–SD, and SR–RD fading channels. In addition, we perform the exact outage probability analysis for the same scenario. Furthermore, we provide the asymptotic expressions for SEP and outage probability by removing the infinite-series terms to investigate the diversity order. In a nutshell, the numerical results reveal that the SR–RD correlated channel scenario outperforms the uncorrelated channel scenario in terms of SEP. In addition, SEP performance degradation is observed in the case of other correlated channel scenarios compared with the uncorrelated channel scenario. Moreover, marginal performance improvement in outage probability is observed in the low-signal-to-noise-ratio (SNR) regime of the SR–RD correlated channel scenario compared with the uncorrelated channel scenario. Finally, Monte Carlo simulations are performed to validate the theoretical results

Performance comparison of selection combining with full CSI and switch-and-examine combining with and without post-selection

Selection combining (SC) with full channel state information (CS!) achieves full diversity order in a decode-and-forward (DF) relaying system. However, the estimation of CSI of all the links is a cumbersome process. As an alternative, switched-diversity techniques have been proposed in the literature, in which CSI of all the links are not simultaneously required. In this paper, we compare the variants of the switched-diversity and full-CSI SC schemes through a paired error approach for a multiDF-relaying-based cooperative diversity system. We derive the exact symbol error probability (SEP) expressions for the full-CSI SC, switch-and-examine combining (SEC), and SEC with postselection (SECps) schemes, considering M-ary phase-shift keying (MPSK) signaling over slow, flat, independent, and nonidentical Nakagami-m fading channels. It is to be noted that the derived SEP expressions are valid for integer values of fading severity parameter m. In addition, we also present the closed-form asymptotic SEP expressions for MPSK signaling to evaluate the diversity order. Concisely, from the numerical results, it is observed that the SECps scheme is able to offer the same performance as that of the full-CSI SC scheme. Furthermore, the SECps scheme outperforms the SEC scheme with more CSI

Performance analysis of triple correlated selection combining for cooperative diversity systems

In this paper, we analyse the performance of a single-relay cooperative diversity system, which is an effective technique to combat the effects of small scale fading, in a more realistic scenario by assuming a correlation among source-to-relay (SR), relay-to-destination (RD), and source-to-destination (SD) links. A generalised closed form end-to-end symbol error probability (SEP) expression for M-ary phase-shift keying (MPSK) scheme using paired error approach has been derived over correlated Nakagami-m fading channels with decode and forward (DF) protocol being used at the relay node. Moreover, we use similar error approach to analyse the performance of a double correlated cooperative diversity system by assuming the correlation between SR and RD channels. Finally, Monte Carlo simulation has been performed to validate the theoretical results.Accepted versio