Log-Likelihood Ratio Calculation for Pilot Symbol Assisted Coded Modulation Schemes With Residual Phase Noise

Word-orthogonal frequency division multiplexing (UW-OFDM) is known to provide various performance benefits over conventional cyclic prefix (CP) based OFDM. Most important, UW-OFDM features excellent spectral sidelobe suppression properties and an outstanding bit error ratio (BER) performance. Carrier frequency offset (CFO) induced impairments denote a challenging task for OFDM systems of any kind. In this work we investigate the CFO effects on UW-OFDM and compare it to conventional multi-carrier and single-carrier systems. Different CFO compensation approaches with different computational complexity are considered throughout this work and assessed against each other. A mean squared error analysis carried out after data estimation reveals a significant higher robustness of UW-OFDM over CP-OFDM against CFO effects. Additionally, the conducted BER simulations generally support this conclusion for various scenarios, ranging from uncoded to coded transmission in a frequency selective environment.

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“…For the calculation of the bit LLRs fed to the decoder, we rely on the derivations in [45], which assume as underlying model…”

Section: Appendix a Derivation Of Signaling Model For Llr Calculationmentioning

confidence: 99%

Impact of a Carrier Frequency Offset on Unique Word OFDM

Hofbauer

Haselmayr

Bernhard

et al. 2020

2020 IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications

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“…To the best of author's knowledge, this work is the first to address these issues in the LDPC-CMSs used in PtPMRLs. It is worth noting that in addition to the contributions presented in the previous chapters, we proposed a novel LLR calculation in [34]. This scheme is integrated into the chipset of one of the PtP backhaul products manufactured by Huawei Technologies.…”

Section: Discussionmentioning

confidence: 99%

“…In the literature, the variance of the increment, σ 2 λ φ , is found using the formula σ 2 λ φ = 2πβT s , where β is the 3-dB linewidth of the PN [30]. In [34], we derived an alternative novel formula for calculating σ 2 λ φ using PN measurements. An example of PN samples generated according to the Wiener model is provided in Fig.…”

Section: Wiener Phase Noise Modelmentioning

confidence: 99%

“…, where L is the PN level at frequency offset f 0 from the carrier frequency [34]. The parameter t can be any time instance, e.g., when a pilot symbol is sampled at the output of the matched filter.…”

Section: Characterization Of Zmentioning

confidence: 99%

“…The (k −1)m+l-th entry of Λ, which corresponds to the l-th LLR of the k-th received signal, R k , can be approximated by [34]:…”

Section: Application Of MC and Is Schemes For Fer Estimation In Ldpc Codesmentioning

confidence: 99%

See 2 more Smart Citations

Performance Enhancement of High Order LDPC Coded Modulation Systems with Application in Mobile Backhaul Networks

Neshaastegaran¹

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Wireless backhaul communication systems play a crucial role in the infrastructure of current cellular networks. In light of the expensive costs of fiber deployment, the importance of these links is anticipated to continue over the next few decades.Point-to-point microwave radio links (PtPMRLs) are the backbone of every wireless backhaul system. To achieve higher spectral efficiencies, the PtPMRL are designed based on the concurrent exploitation of high-order modulations and powerful forward error correcting codes. An example of such design paradigm is the high-order lowdensity-parity-check coded modulation systems (LDPC-CMSs). In this thesis two key challenges in the high-order LDPC-CMSs are overcome.In our first contribution, we consider the problem of oscillator phase hit (PH) in microwave backhaul communication links. PH results in a temporary link loss in the communication system and bears an expensive cost on the operators. In this work, we propose a two-stage solution to mitigate PH. In the first stage, we use Neyman-Pearson binary hypothesis testing to develop a low cost PH detection algorithm.In this test, a likelihood ratio test is designed and the optimal detection threshold is analytically calculated. The proposed PH detection scheme entails small real-time computations while using the existing pilot symbols in the system; thus, no extra pilot overhead is required. In the second stage, we use maximum likelihood estimation to develop a PH correction scheme. In particular, we formulate the joint estimation of phase noise (PN) and PH as a maximum likelihood estimation problem. Solving this problem results in the estimation of PN with the location and magnitude of PH. By applying the proposed correction scheme, the number of affected symbols by PH is significantly reduced. In particular, the number of remaining erroneous symbols due to PH (if any) is within the error correction capability of modern LDPC codes used iii Table of Contents viii List of Tables xi List of Figures xiii List of References 103Appendix A

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