Improved Maximum Access Delay Time, Noise Variance, and Power Delay Profile Estimations for OFDM Systems

Abstract

In this paper, we propose improved maximum access delay time, noise variance, and power delay profile (PDP) estimation schemes for orthogonal frequency division multiplexing (OFDM) system in multipath fading channels. To this end, we adopt the approximate maximum likelihood (ML) estimation strategy. For the first step, the log-likelihood function (LLF) of the received OFDM symbols is derived by utilizing only the cyclic redundancy induced by cyclic prefix (CP) without additional information. Then, the set of the initial path powers is sub-optimally obtained to maximize the derived LLF. In the second step, we can select a subset of the initial path power set, i.e. the maximum access delay time, so as to maximize the modified LLF. Through numerical simulations, the benefit of the proposed method is verified by comparison with the existing methods in terms of normalized mean square error, erroneous detection, and good detection probabilities.

Near-Optimal Low-Complexity Hybrid Precoding for THz Massive MIMO Systems

“…The base station (BS) is equipped with t N transmitting antennas and RF N RF chains to serve users, while each user is equipped with r N receiving antennas. The system adopts MIMO-assisted orthogonal frequency-division multiplexing (OFDM) modulation with K subcarriers [14]. For each subcarrier, the BS transmits s N data streams to the receiver, typically with…”