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Orthogonal frequency division multiplexing (OFDM) systems require the knowledge of signal-to-noise ratio (SNR) at the receiver in order to maximize the system performance. In general, the noise variance is required by the SNR estimator and the knowledge of noise variance also improves the performances of carrier frequency offset (CFO) and channel state estimations. This paper first investigates the...
Orthogonal frequency division multiplexing (OFDM) systems require the knowledge of signal-to-noise ratio (SNR) at receiver in order to maximize system performance. In general, SNR can be estimated with the help of noise variance. The existing literatures mostly assume that noise variance is estimated in the case of that channel status information (CSI) is known in advance and synchronization is perfectly...
Bandwidth efficiency is a critical concern in wireless communications. To fully utilize the available bandwidth, this paper adopts the superimposed training (ST) scheme in orthogonal frequency division multiplexing (OFDM) systems without using cyclic prefix (CP) and guard interval (GI). If the pilot pattern is fixed, it is shown that the performance of the channel estimation using the ST scheme is...
In orthogonal frequency division multiplexing (OFDM) systems, the equally-powered pilots (EPP) scheme is known to provide the best channel estimation performance when the channel status is unknown. In this study, it is shown that if we assume the channel correlation function (CCF) of a quasistatic channel is perfectly known at the receiver, all of the available pilot power should be allocated to the...
This paper considers the joint symbol detection and channel estimation problem for cooperative communications in cluster-based networks. The proposed joint detection and estimation scheme is derived by using the expectation maximization (EM) algorithm. In addition, the cooperative communication between the relays and the destination is based on the concept of compress-and-forward (CF) scheme. Most...
One of the major drawbacks of the orthogonal frequency division multiple access (OFDMA) system is the multi-user interference (MUI) induced by the carrier frequency offsets (CFOs). In sub-band based OFDMA systems, users occupy consecutive and non-overlapping frequency sub-bands. The pilots are usually placed on the edges of a sub-band for channel estimation. However, the channel estimation performance...
The existing papers have proposed the Call Admission Control (CAC) arithmetic based on resource reservation, which only considered ideal environment, for CDMA cellular systems with no-uniform traffic distribution among cells. This paper extends the arithmetic to intra-cell unbalanced traffic environment to make the arithmetic more practical. The inter-cell interference factor is not a constant and...
A superimposed training scheme is proposed for channel estimation in OFDM systems. The generalized chirp-like (GCL) sequence is adopted since it has a constant magnitude in both the time domain and the frequency domain. Although the derived channel estimator has a slightly worse performance since the unknown data contributes extra noise, the effective data throughput is substantially increased. In...
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