Designing unique words for near‐optimal training in block transmission systems

Abstract

SUMMARYIn this paper, we consider the problem of designing unique words (UWs) in single-carrier block transmission systems for the purpose of performing bandwidth efficient channel estimation. By first deriving the Cramér-Rao lower bound (CRLB) for the UW-based channel estimator, we show that designing optimal UWs reduces to a problem of constructing sequences of length Q ≤ N/2 that, when padded with zeros to make a length-N sequence, have good periodic autocorrelation properties. We then show that the only class of short (length-Q) sequences that, when padded with N − Q zeros, have perfect periodic autocorrelation properties is the class of Kronecker delta sequences. Due to the fact that these sequences typically suffer from a high peakto-average power ratio (PAPR), we then formulate two optimisation procedures to find near-optimal UWs under certain constraints. Finally, we show that the sequences that are found with the proposed technique perform significantly better than Kronecker delta sequences that have been scaled to meet a given PAPR constraint.

A Generalized Prefix Construction for OFDM Systems Over Quasi-Static Channels

“…This makes comparisons under identical assumptions difficult. For example, the design of UW is considered subject to a constraint on the peak-to-average power ratio (PAPR) [12]. In KSP-OFDM, the KSP part is not part of DFT, similar to CP-OFDM, but performance simulations reported in [13] show that KSP-OFDM suffers from noise enhancement and has a slightly worse performance than CP-OFDM.…”

Non-Linear Optimization of IEEE802.11e Super-frame Configuration

“…The various methods within non-linear optimization theory optimize (as the name suggests) any number of variable parameters to provide a stable system solution. Non-linear optimization has been applied to various problem domains within communications, including wireless sensor network access [4] and deriving training sequences for orthogonal frequency division multiplexing (OFDM) systems [5,6]. We use the barrier method [7] in this work.…”