Robust Frame and Frequency Synchronization Based on Alamouti Coding for RGI-CO-OFDM

Omomukuyo, Oluyemi; Chang, Deyuan; Dobre, Octavia A.; Venkatesan, R.; Ngatched, Telex M. N.

doi:10.1109/lpt.2016.2623322

Cited by 7 publications

(5 citation statements)

References 15 publications

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“…The DSP in the transmitter performs functions such as encoding, pulse shaping and pre-distortion, while the DSP in the receiver is used for impairment mitigation, clock recovery, synchronization etc. [26]. The coherent detector and the IQ modulator are expected to be pluggable modules.…”

Section: ) Sbvt Architecturementioning

confidence: 99%

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

Imran

Anandarajah

Kaszubowska-Anandarajah

et al. 2018

IEEE Commun. Surv. Tutorials

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Abstract-Elastic optical networks (EON) have been proposed to meet the network capacity and dynamicity challenges. Hardware and software resource optimization and re-configurability are key enablers for EONs. Recently, innovative multi-carrier transmission techniques have been extensively investigated to realize high capacity (Tb/s) flexible transceivers. In addition to standard telecommunication lasers, optical carrier generators based on optical frequency combs (OFC) have also been considered with expectations of reduced cost and inventory, improved spectral efficiency and flexibility. A wide range of OFC generation techniques have been proposed in the literature over the past few years. It is imperative to summarize the state of the art, compare and assess these diverse techniques from a practical perspective. In this survey, we identify salient features of optical multicarrier generators, review and compare these techniques both from a physical and network layer perspective. OFC demultiplexing/filtering techniques have also been reviewed. In addition to transmission performance, the impact of such sources on the network performance and real-world deployment strategies with reference to cost, power consumption, and level of flexibility have also been discussed. Field trials, integrated solutions, flexibility demonstrations are also reported. Finally, open issues and possible future directions that can lead to real network deployment are highlighted.

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Section: ) Sbvt Architecturementioning

confidence: 99%

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

Imran

Anandarajah

Kaszubowska-Anandarajah

et al. 2018

IEEE Commun. Surv. Tutorials

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“…The training symbols 𝐴 and 𝐵, of length 𝑁 𝑠𝑐 , where 𝑁 𝑠𝑐 is the number of OFDM subcarriers, are zero-padded with 𝑁 − 𝑁 𝑠𝑐 zeros, where 𝑁 is the inverse fast Fourier transform (IFFT) size. The starting point of the frame for the x-polarization, 𝑑 ̂𝑥, can be determined by utilizing the autocorrelative property of the GCS to construct a timing metric [8]: where 𝑟 𝑥 (𝑑) and 𝑟 𝑦 (𝑑) are the discrete received samples for the x and y polarizations, respectively, 𝛼 is the PMD-induced delay (in samples), 𝑁 𝑐𝑝 is the number of cyclic prefix samples, 𝑚𝑜𝑑(. ) is the modulo operator, and 𝑝(𝑛) ∈ (−1,1], with 𝑛 = 0,1, ⋯ , 𝑁 + 𝑁 𝑐𝑝 − 1, is a pseudo-random sequence used to ensure the timing metric is impulse-shaped with a distinct peak.…”

Section: Frame Synchronizationmentioning

confidence: 99%

“…is the modulo operator, and 𝑝(𝑛) ∈ (−1,1], with 𝑛 = 0,1, ⋯ , 𝑁 + 𝑁 𝑐𝑝 − 1, is a pseudo-random sequence used to ensure the timing metric is impulse-shaped with a distinct peak. The interested reader is referred to [8] for similar equations for the y-polarization.…”

Section: Frame Synchronizationmentioning

confidence: 99%

“…The frequency synchronization is divided into two sub-stages: fractional frequency synchronization, for estimating the fractional part of the CFO with a magnitude ≤ ∆𝑓, and integer frequency synchronization, for estimating the integer part of the CFO, where ∆𝑓 is the OFDM subcarrier spacing. After obtaining the right start of the CO-OFDM frame, the estimate of the fractional CFO is obtained from (1) by setting 𝛼 = 0 and 𝑑 = 𝑑 ̂𝑥, as explained in detail in [8].…”

Section: Frequency Synchronizationmentioning

confidence: 99%

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Bandwidth-efficient synchronization for fiber optic transmission: system performance measurements

Omomukuyo

Dobre

Venkatesan

et al. 2017

IEEE Instrum. Meas. Mag.

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By any measure, the various services and applications which are crucial to today's society rely on fast, efficient, and reliable information exchange. Nowadays, most of this information traffic is carried over long distances by optical fiber, which has intrinsic advantages such as wide transmission bandwidth and low attenuation. However, continuing traffic growth has imposed many challenges, especially for equipment manufacturers who have to develop optical transmission solutions to handle the demand for higher data rates without incurring increased capital and operational costs. A feasible approach to overcoming these challenges is to scale the channel capacity by employing orthogonal frequency division multiplexing (OFDM) superchannels. However, OFDM is sensitive to synchronization errors, which can result in complete failure of the receiver-based digital signal processing. Measurement results of various existing OFDM synchronization methods have highlighted inherent limitations with regards to poor system performance, which determines the quality-of-service level perceived by the end user, and complexity, which throws doubts as to their suitability for implementation in actual equipment. In this article, we first provide a brief overview of optical transmission systems and some of their performance specifications. We then present a simple, robust, and bandwidth-efficient OFDM synchronization method, and carry out measurements to validate the presented synchronization method with the aid of an experimental setup.

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“…Welch bound [25] of -16 dB. These short-codes may not find practical applications for sonar, but they may be useful in other applications such as frame preambles for synchronisation [226][227][228].…”

Section: Masks For a Wider Mainlobementioning

confidence: 99%

Code Optimisation Framework for Multicode Sonar Systems

Rashed¹

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<p>The ocean is a temporally and spatially varying environment, the characteristics of which pose significant challenges to the development of effective underwater wireless communications and sensing systems. An underwater sensing system such as a sonar detects the presence of a known signal through correlation. It is advantageous to use multiple transducers to increase surveying area with reduced surveying costs and time. Each transducers is assigned a dedicated code. When using multiple codes, the sidelobes of auto- and crosscorrelations are restricted to theoretical limits known as bounds. Sets of codes must be optimised in order to achieve optimal correlation properties, and, achieve Sidelobe Level (SLL)s as low as possible. In this thesis, we present a novel code-optimisation method to optimise code-sets with any number of codes and up to any length of each code. We optimise code-sets for a matched filter for application in a multi-code sonar system. We first present our gradient-descent based algorithm to optimise sets of codes for flat and low crosscorrelations and autocorrelation sidelobes, including conformance of the magnitude of the samples of the codes to a target power profile. We incorporate the transducer frequency response and the channel effects into the optimisation algorithm. We compare the correlations of our optimised codes with the well-known Welch bound. We then present a method to widen the autocorrelation mainlobe and impose monotonicity. In many cases, we are able to achieve SLLs beyond the Welch bound. We study the Signal to Noise Ratio (SNR) improvement of the optimised codes for an Underwater Acoustic (UWA) channel. During its propagation, the acoustic wave suffers non-constant transmission loss which is compensated by the application of an appropriate Time Variable Gain (TVG). The effect of the TVG modifies the noise received with the signal. We show that in most cases, the matched filter is still the optimum filter. We also show that the accuracy in timing is very important in the application of the TVG to the received signal. We then incorporate Doppler tolerance into the existing optimisation algorithm. Our proposed method is able to optimise sets of codes for multiple Doppler scaling factors and non-integer delays in the arrival of the reflection, while still conforming to other constraints. We suggest designing mismatched filters to further reduce the SLLs, firstly using an existing Quadratically Constrained Qaudratic Program (QCQP) formulation and secondly, as a local optimisation problem, modifying our basic optimisation algorithm.</p>

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Robust Frame and Frequency Synchronization Based on Alamouti Coding for RGI-CO-OFDM

Cited by 7 publications

References 15 publications

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

Bandwidth-efficient synchronization for fiber optic transmission: system performance measurements

Code Optimisation Framework for Multicode Sonar Systems

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