Pilot-free common phase error estimation for CO-OFDM with improved spectral efficiency
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Cites methods from "Pilot-free common phase error estim..."
...The received data is first conjugated, processed using the standard CO-OFDM DSP algorithms [33] and the performance of the same is evaluated as a function of the OSNR as shown in Fig....
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...The digitized output is post-processed using off-line digital signal processing (DSP) algorithms, which includes (correlation-based) time and (blind) frequency synchronization, training symbols based channel estimation/ equalization and pilot subcarriers assisted phase noise correction [33]....
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References
355 citations
"Pilot-free common phase error estim..." refers background in this paper
...However, due to the longer symbol duration (Ts), the CO-OFDM system is more susceptible to phase noise due to laser linewidth ( ν2 ) and hence suffers performance degradation due to common phase error (CPE) and inter carrier interference (ICI) [4]....
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...N F F T and N F F T is the number of subcarriers; Ym (k), Xm (k), I C I m (k) and Wm (k) represent the received signal, transmitted signal, Inter Carrier Interference (ICI) and AWGN terms respectively in the kth sub-carrier of the mth OFDM symbol....
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...This algorithm can be further extended by modifying and incorporating equalization for the effect of ICI and the state vector of the Kalman filter can also take additional parameter to estimate and correct the residual frequency offset, if any....
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...However, due to the longer symbol duration (Ts), the CO-OFDM system is more susceptible to phase noise due to laser linewidth ( ν 2 ) and hence suffers performance degradation due to common phase error (CPE) and inter carrier interference (ICI) [4]....
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...The ICI component due to phase noise is described as I C Im (k) = N F F T −1∑ l=0, l =k Xm (l)Im (l − k), (2) with Im (p ) = 1N F F T N F F T −1∑ n=0 e j [ 2πp n N F F T +φm (n) ] (3) where Im (0) is the common phase error (CPE) factor given as Im (0) ≈ exp (jφ(m)) and φ(m) is the CPE across the subcarriers of the mth OFDM symbol given as φ(m) = arg { 1 N F F T N F F T −1∑ n=0 e jφm (n) } ....
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264 citations
"Pilot-free common phase error estim..." refers background in this paper
...Coherent optical OFDM (CO-OFDM) is one such multi-carrier scheme that is comprehensively investigated in optical communication systems as an alternate to Nyquist pulse shaped single carrier transmission for >Terabit/s transmission and inelastic optical networks [2]....
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58 citations
"Pilot-free common phase error estim..." refers background in this paper
...CO-OFDM also has extreme tolerance to linear fiber impairments such as chromatic dispersion and polarization mode dispersion and hence enables simple equalization [3]....
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49 citations
"Pilot-free common phase error estim..." refers background or methods in this paper
...Non-pilot aided zero-overhead CPE estimations were proposed in [7], [8] by using higher order statistics and decision directed (DD) iterative algorithms....
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...For instance, [7] estimated the complexity of the DD algorithm to be almost 28% additional compared to the conventional pilot aided algorithm....
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...The polarization is adjusted to have maximum power coupled in one of the polarization and is then fed to a phase diverse coherent receiver with a local oscillator tuned to 1550 nm and with ν ≈ 50 KHz....
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...In this method these pilots are used at the receiver to estimate the CPE as [7], [8]...
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...In addition, DD-CPE algorithms inherit error propagation when the initialization is erroneous or when the laser linewidth is large (>100 KHz) [7]....
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32 citations
"Pilot-free common phase error estim..." refers methods in this paper
...In such square MQAM baseband modulated data, a multi-level QPSK partitioning [10] is performed to extract the outermost and the innermost QPSK points from the constellation....
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