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In this paper we propose a robust channel estimator for Long Term Evolution (LTE) downlink highly selective using neural network. This method uses the information provided by the reference signals to estimate the total frequency response of the channel in two phases. In the first phase, the proposed method learns to adapt to the channel variations, and in the second phase it predicts the channel parameters...
A crucial parameter required for adaptive transmission in orthogonal frequency division multiplexing (OFDM) systems is the signal-to-noise ratio (SNR). In this paper, certain modifications to previously proposed preamble-based SNR estimator for wireless OFDM systems are suggested in order to improve estimation performance. Proposed modifications, related to DFT interpolation, are based on the adaptive...
In future wireless communication systems like LTE, wide bandwidths for the transmission of high data rates result in frequency selective mobile radio channels. If data transmission takes place at high mobile speeds the mobile radio channel becomes also time selective. In this paper we propose for the estimation of such double selective channels a modification to the well known complex exponential...
Cooperative communication offers a way to obtain spatial diversity in a wireless network without increasing hardware demands. The different cooperation protocols proposed in the literature are often studied under the assumption that all channel state information is available at the destination. In a practical scenario, channel estimates need to be derived from the broadcasted signals. In this paper,...
This paper tackles the problem of fast varying channel estimation in LTE systems. Particular attention is given to downlink transmission where OFDMA is used as the multiple access technique for the air interface. In OFDMA, fast variation of the channel results in significant inter-carrier interference (ICI) which cannot be mitigated with conventional estimation and equalization techniques. In this...
The estimation of the position of an emitting source is an important aspect of emerging cognitive radio systems. We readdress the known problem of estimating the Direction-of-Arrival (DOA) of an emitting source via passive radio means, namely an antenna array. The challenges in the considered scenarios are (a) time-varying, terrestrial multipath propagation with medium-to-low SNR and (b) very short...
This paper presents a new blind symbol timing offset (STO) estimation scheme for wireless orthogonal frequency division multiplexing (OFDM) systems with constant modulus constellation. In the proposed scheme, the STO estimation is performed by minimizing the power difference between either adjacent or consecutive subcarriers, which basically depends on the assumptions made on the channel conditions...
Channel coherence time is commonly used to characterize the rate at which the channel changes. The recently introduced effective coherence time measures the channel change rate from an estimation perspective. It was shown that the effective coherence time is related to the capacity of the non-coherent channel, in which the receiver has no prior knowledge of the channel, and tries to estimate it from...
Base station cooperation is a promising solution to the interference limitation of today's cellular networks. The capacity and fairness gains shown by information theoretical analysis of base station cooperation in cellular networks are huge. However, a major downside is the information exchange among base stations, which is the motivation for recent work on backhaul efficient cooperation schemes...
In densely deployed sensor networks, correlation among measurements may be high. Spatial sampling through node selection is usually used to minimize this correlation and to save energy consumption. However because of the fading nature of the wireless channels, extra care should be taken when performing this sampling. In this paper, we develop expressions for the distortion which include the channel...
Estimation of single-carrier communication channels based on superimposed training (ST) has been widely studied in the last years, because it offers a way for estimating the channel without the transmission of a pilot sequence multiplexed in time with the data, which implies a saving of valuable bandwidth. In this paper, the use of a variation of ST known as data-dependent superimposed training (DDST)...
In this paper, optimal training design and placement are studied for channel estimation in a frequency selective, single relay, amplify and forward cooperative system. Using a two-phase transmission protocol, the power distribution between the phases, among the pilot tones as well as the positioning of pilot tones within the transmitted OFDM symbols are examined. The LMMSE and two variants of the...
Adaptive modulation and code (AMC) in Orthogonal Frequency Division Multiplexing (OFDM) is a promising approach to achieve higher data rates with sufficient performance. However a measure of channel state is desired in order to decide upon transition rates and modulation mode. SNR is such a sufficient measure. In this work, a channel estimator based on transform domain algorithm (TFD) is presented...
Consider a first order, linear and time-invariant discrete time system driven by Gaussian, zero mean white process noise, a pre-processor that accepts noisy measurements of the state of the system, and an estimator. The pre-processor and the estimator are not co-located, and, at every time-step, the pre-processor sends either a real number or an erasure symbol to the estimator. We seek the pre-processor...
Network link capacity (lc) and available bandwidth (av-bw) are recently considered as importance for various network domains. Consequently, several lc and av-bw measurement techniques and tools have been proposed, where empirical experience, performance comparison and foundational understanding of lc/av-bw measurement have been focused. Many heuristic or non-probabilistic statistical algorithms have...
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