Synchronization, Channel Estimation, and Equalization in MB-OFDM Systems

Abstract

Abstract-This paper addresses preamble-based low complexity synchronization, channel estimation and equalization for Zero-padded (ZP) MB-OFDM based UWB systems. The proposed synchronization method consists of sync detection, coarse timing estimation, fine timing estimation, and oscillator frequency offset estimation. The distinctive features of MB-OFDM systems and the interplay between the timing and carrier frequency hopping at the receiver are judiciously incorporated in the proposed synchronization method. In order to apply the low complexity one-tap frequency-domain equalizer, the required circular convolution property of the received signal is obtained by means of an overlap-add method after the frequency offset compensation. The proposed low complexity channel estimator for each band is developed by first averaging the over-lapadded received preamble symbols within the same band and then applying time-domain least-squares method followed by the discrete Fourier transform. We develop an MMSE equalizer and its approximate version with low complexity. We also derive the probability density functions of the UWB channel path delays, and using them we present several optimization criteria for our proposed synchronization, channel estimation, and equalization. The effectiveness of our proposed methods and optimization criteria are confirmed by computer simulation results.

A Comprehensive Study of Channel Estimation for WBAN-based Healthcare Systems: Feasibility of Using Multiband UWB

“…The low complexity channel estimator [11] for each band is developed by first averaging the over-lap-added (OLA) received preamble symbols within the same band and then applying time-domain least-squares method followed by the discrete Fourier transform. Specifically, for every lth nonzero OFDM symbol in the qth band after CFO compensation, the OLA method adds M 0 s a m p l e s b r q k ft þ lM þ N…”

“…Similarly, TFCE (Eqs. (9) and (11)) and IICE (Eq. (16)) need N 3 and N 2 multiplications, respectively.…”

Low-complexity WLMMSE channel estimator for MB-OFDM UWB systems

“…A collection of problems including channel measurements and modeling, channel estimation, and synchronization have been widely studied by researchers [5][6][7][8][9][10]. Clearly, all the performance improvement and capacity increase are based on accurate channel state information.…”

“…In the UWB literature, the channel estimation has mostly been studied for its effect on error rate performance and computational complexity [8][9][10][11][12][13][14][15][16][17][18]. For example, a minimum mean square error (MMSE) estimator has been proposed by Beek et al, and they have shown that it gives a performance gain over least square (LS) estimator [8].…”

“…For example, a minimum mean square error (MMSE) estimator has been proposed by Beek et al, and they have shown that it gives a performance gain over least square (LS) estimator [8]. Moreover, Li et al have proposed a low-complexity channel estimator developed by first averaging the overlap-added (OLA) received preamble symbols within the same band and then applying time-domain least squares method followed by the discrete Fourier transform [9]. Also, a low-sampling-rate scheme, based on multiple observations generated by transmitting multiple pulses, for ultra-wideband channel estimation has been proposed in [12].…”