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Wireless communication using very-large multiple-input multiple-output (MIMO) antennas is a new research field, where base stations are equipped with a very large number of antennas as compared to previously considered systems. In theory, as the number of antennas increases, propagation properties that were random before start to become deterministic. Theoretical investigations with independent identically...
In this work we present a new low-power medium access scheme for sensor-type networks specifically with low traffic intensity. We call the proposed scheme DCW-MAC where ultra-low-power wake-up receivers are combined with optimal duty-cycled listening. First we introduce a framework for the analysis of energy consumption of the studied network type, then we use it to optimize the MAC scheme to achieve...
Multiple-input multiple-output (MIMO) is a mandatory feature of the Third Generation Partnership Project (3GPP) Long Term Evolution. This work investigates the performance of a low complexity channel estimator for LTE terminals with an emphasis on the 4 × 4 multiple antenna scheme. The presented work extends a promising low-complexity 2 × 2 MIMO channel estimator to the 4×4 MIMO case and evaluates...
This paper describes a novel approach to a Matched Pursuit LTE Channel Estimator. It is shown that the total complexity of the estimator can be reduced by, perhaps counter-intuitively, increasing the resolution of the estimator, since for certain choices of resolution a number of multiplication factors will be zero. An architecture is presented that implements the novel algorithm. By increasing the...
This paper presents a novel memory optimization technique to exploit the analogy between correlation coefficients in MMSE-based channel estimators across multiple standards. The need for coefficient storage for robust MMSE channel estimators is expensive in terms of on-chip memory. Besides, the memory requirements grow linearly by integrating more standards onto one platform. Thus, it becomes inevitable...
This paper proposes two low-complexity two-dimensional channel estimators for MIMO-OFDM systems derived from a joint time–frequency channel estimator. The estimators exploit both time and frequency correlations of the wireless channel via use of Slepian-basis expansions. The computational saving comes from replacing a two-dimensional Slepian-basis expansion with two serially concatenated one-dimensional...
In this paper a number of low-complexity channel estimator structures tailored to the needs of LTE terminals have been investigated. The focus has been on the algorithms exhibiting reduced complexity while providing an acceptable level of performance. To design these estimators other factors such as interoperability with another OFDM-based standard, DVB-H, in a multi-standard environment have been...
In this paper we evaluate the use of parallel interleavers for user separation in coded IDMA systems. The parallel interleavers have previously been evaluated for uncoded systems, and we here present extended results for the coded case. The new results are important for real systems, as they will most likely use performance enhancing channel coding. The parallel interleavers are designed to remove...
In this paper we analyze the performance of three low-complexity channel estimators, based on the discrete Fourier transform (DFT), for orthogonal frequency-division multiplexing (OFDM) systems. Estimators of this type have been analyzed for discrete-time channels, and we extend this analysis to continuous-time channels. We present analytical expressions for their mean-squared error (MSE) and evaluate...
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