Concatenated Precoded OFDM for CFO Effect Mitigation

Abstract

Orthogonal frequency-division multiplexing (OFDM) is highly sensitive to carrier frequency offset (CFO), which not only causes intercarrier interference (ICI) among subcarriers but introduces complex multiplicative distortion (CMD) to all detected subcarrier symbols as well. Due to unknown CFO, both ICI and CMD are time variant, thus complicating the data demodulation at the receiver. In conjunction with a training-prefixed data frame structure, a concatenated precoder that is constructed by concatenating an outer modified correlative precoder with an inner reduced Hadamard precoder is proposed in this paper to process data symbols prior to OFDM modulation and to enable joint estimation on channel multipath and constant CMD (CCMD), time-variant CMD (TCMD) estimation and compensation, and ICI suppression at the receiver in the presence of CFO. Simulation results show that the proposed system provides much better error performance than conventional signal coding approaches in the presence of CFO and multipath fading.Index Terms-Carrier frequency offset (CFO), correlative code, Hadamard code, intercarrier interference (ICI), orthogonal frequency-division multiplexing (OFDM).

Timing and carrier synchronization in wireless communication systems: a survey and classification of research in the last 5 years

“…Also, they consider the same problem in terms of estimation or compensation. In the [50], [103], [119], [120], [127], [133], [145], [146], [148], [162], [173], [178], [181], [182], [186], [191], [196] Freq. sel.…”

“…The first group does not provide an estimation error lower bound [50,103,119,120,127,133,145,146,148,162,173,178,181,182,186,191,196]. In addition to carrier synchronization, [50] proposes to achieve seamless service in vehicular communication and also considers road side unit selection, [103] considers CFO tracking assuming constant modulus based signaling, [119] considers concatenated precoded OFDM system, [120] proposes MMSE based estimation, [127] proposes hard decision directed based CFO tracking, [133] considers phase rotated conjugate transmission and receiver feedback, [145] considers hardware implementation with IQ imbalance and power amplifier nonlinearity, [146] considers hexagonal multi-carrier transmission system and a doubly dispersive channel, [148] considers maximum a posteriori expectation-maximization (MAP-EM) based Turbo receiver, [162] considers an FBMC system, [173] considers aerial vehicular communication, [178] proposes noise variance estimation and considers EM algorithm, [181] considers SFO estimation, [182] considers hardware implementation, [186] proposes estimation of the CFO over a wide range of offset values, [191] considers IQ imbalance and phase noise distortion, and [196] considers Doppler spread in a mobile OFDM system. The second group of papers provides an estimation error lower bound on obtaining the CFO [79,90,…”

Sparse-training-sequence-aided OFDM systems for CFO effect mitigation

“…Although the effect of constant distortion E (h) is compensated, the TCMD ( ) ( ) still remains and signi cantly degrades the system performance [7]. To suppress the effect of ( ) ( ) in x ( )0 , a LS-based TCMD estimation using transmitted pilot symbols is then developed to facilitate the data detection in conjunction with ( ) ( ) compensation.…”

A Novel Two Stage Carrier Frequency Offset Estimation and Compensation Scheme in Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing System Using Expectation and Maximization Iteration

“…It is known from (Yue et al, 2007) that CFO will cause severe Inter Carrier Interference (ICI) in OFDM which degrades the system performance. The impact of CFO on OFDM is estimated in (Tseng and Chung, 2013). A time domain method was proposed in (Chung and Phoong, 2010) for the estimation of CFO in MIMO OFDM system.…”