Joint Frequency-Domain Equalization and Channel Estimation Using Superimposed Pilots

Abstract

SC modulations (Single-Carrier) with FDE (Frequency-Domain Equalization) are promising candidates for future broadband wireless systems. These modulations allow excellent performances in severely time-dispersive channels, provided that accurate channel estimates are available at the receiver. For this purpose, pilot symbols and/or training sequences are usually multiplexed with data symbols. Since this leads to overhead and some spectral degradation, the use of superimposed pilots (i.e., pilots added to data) was recently proposed.In this paper we consider SC-FDE systems where the channel estimation is based on superimposed pilots. Since the interference levels between data and pilots might be very high, we propose an iterative receiver with joint equalization and channel estimation. Our performance results show that the use of superimposed pilots, combined with the proposed receiver, allows performances close to the case with perfect channel estimation, even for severely time-dispersive channels. 1

Novel signal reconstruction method for SC-FDE systems with frequency domain pilot multiplexing technique over time-varying channels

“…From (6), it is clear that the ISR method compensates for the loss data tones in an iterative manner to improve the accuracy of the data estimates. However, the incorrect or imperfect compensation for the loss data tones will have a negative effect on the data estimates and may incur the problem of error propagation, which will be clarified in the simulations.…”

Channel estimation with iterative discrete Fourier transform‐based smoothing for orthogonal frequency‐division multiplexing systems with non‐uniformly spaced pilots in channels with long delay spread

“…In addition, the method in [15][16][17] is mainly for systems with a training block [15,17] or with superimposed pilots [15] in the frame. Therefore, it is not obvious how to directly apply the concept in [15][16][17] to a pilot-assisted OFDM system, such as the WiMAX system. For this problem, we have a clear explanation (see also Section 4).…”

“…From (15) to (17), it is clear that we are unable to obtain the correct impulse response because of non-uniform sampling. If uniform sampling was used, the term e −j(2π/7M )(3m − 3.5n) in (14) would be ±1, and thus correct result could be obtained.…”

Performance evaluation of time-multiplexed and data-dependent superimposed training based transmission with practical power amplifier model

“…For a reader interested in a pure SI training with iterative reception, a good starting point is, for example, [23]. In this article a computationally efficient, iterative frequency-domain equalization and channel estimation is presented.…”

“…Nonetheless, when there is symbol level limiter involved, we could feedback the cyclic mean of the limiter error estimate in order to improve the channel estimates with LDDST. In addition, in SISO case or in spatially multiplexed MIMO case, the feedback filtering used also in [23], is of great interest and provides interesting topics for future research.…”