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Emerging wireline transmission systems such as G.fast use bands up to around 200 MHz on short cables. A key enabler for achieving the aspired throughput of several hundred Mbit/s is joint processing of transmit signals in downstream direction as well as joint processing of receive signals in upstream direction through techniques referred to as vectoring. A new challenge in such systems are sudden...
Secret key generation algorithms based on radio channel measurements have been proposed to support private communications. This paper presents methods for calculating upper bounds on the secret key generation rate for realistic channel measurement techniques. Bounds are shown for secret key generation using non-simultaneous channel measurements from each communicating party. Since short measurement...
Interference cancellation is a key design concern for next-generation communication systems. One practical approach is the so-called interference rejection combining (IRC) scheme which treat interference as a stationary Gaussian process to simplify interference suppression design. However, this stationary assumption does not hold in practice; in particular, the statistics of the pilot and the data...
Compressive sensing (CS) has recently attracted lots of attention and has been extended to more structured architectures, for example the linear time-invariant system identification. However, prevalent CS methods used for channel estimation, such as Basis Pursuit Denoising (BPDN) and Dantzig selector (DS), require computational complexity as high as O(N3), where N is the length of the channel. When...
This paper considers the coded OFDM system and instead of discarding the cyclic prefix (CP) at the receiver, we utilize the CP observation for joint detection, decoding and channel estimation. In particular, detection and decoding are performed iteratively between an equalizer and a soft-input soft-output (SISO) decoder based on the turbo principle, and the expectation-maximization (EM) algorithm...
Compared with standard cyclic prefix OFDM (CP-OFDM), time domain synchronous OFDM (TDS-OFDM) can achieve a higher spectrum efficiency by using the known training sequence instead of CP as the guard interval. However, TDS-OFDM suffers from reduced energy efficiency and performance loss due to the existing mutual inferences. In this paper, based on the newly emerging theory of structured compressive...
In this paper, equalization of multihop relaying orthogonal frequency division multiplexing (OFDM) signal is investigated under time-varying channel with unknown noise powers, channel orders and Doppler frequencies. An iterative algorithm is developed under variational expectation maximization (EM) framework. The proposed algorithm iteratively estimates the channel, learns the channel and noise statistical...
We study the massive MIMO (multiple-input multiple-output) multicast transmission in multicell networks, where each base station (BS) is equipped with a large-scale antenna array and transmits a common message using a single beamformer to multiple mobile users. We first consider the case when each BS knows the perfect channel state information (CSI) of all its served users. We show that the asymptotically...
This paper studies the maximum Doppler diversity transmissions in the presence of imperfect channel state information (CSI) in high mobility systems. Due to fast time-varying fading in high mobility systems, channel estimation error is usually inevitable and they might have significant impacts on system performance. On the other hand, Doppler spread caused by fast time-varying fading introduces Doppler...
Cooperative communication systems employ cooperation among nodes in a wireless network to increase data throughput and robustness to signal fading. However, such advantages are only possible if there exist perfect synchronization among all nodes. Impairments like channel multipath, time varying phase noise (PHN) and carrier frequency offset (CFO) result in the loss of synchronization and diversity...
In this paper, we present a sparse channel estimation method for orthogonal frequency division multiplexing (OFDM) based two-way relay networks (TWRN). Conventional channel estimation methods, such as least squares (LS), have been proposed to obtain channel state information (CSI) at the cost of the training resource, which reduce spectrum efficiency. However, physical measurements have verified that...
In this paper, the problem of experiment design for the task of channel identification in cyclic prefixed orthogonal frequency division multiplexing (CP-OFDM) systems is revisited. So far, the optimal input sequences for least squares (LS) channel identification with respect to minimizing the channel mean square error (MSE) under an input energy constraint have been derived. Here, we investigate the...
Collision resolution via interference cancellation (IC) in packet-based random multiple access (RMA) systems is a promising technique to decrease number of retransmissions and increase overall throughput. This paper proposes novel iterative algorithm of IC in OFDM systems for the case when one of the interfering packets is known to the receiver. Comparing to well-known successive interference cancellation...
Generating secret keys from radio channel measurements has been shown to allow private communications. Previously described methods for performing wireless key generation have not come close to achieving the theoretical upper bounds on key rates theory for this technique. This paper demonstrates how using a Kalman filter based on an auto-regressive (AR) model for the channel process, channel gain...
This paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm,...
In this paper, we consider a novel layered coding approach with two layers. One of the two layers, denoted by the base-layer, can be received by any receiver even if it does not have reliable channel estimates. The other, refining-layer can only be received by any receiver that has channel state information. We propose signal constellations that allow the transmission of coherent and non-coherent...
Channel estimation is key to enabling effective multiuser transmission in multiple-input multiple-output cellular networks. Thanks to technology advances and a shift to higher frequency carriers, recently there is an increasing interest in using very large antenna arrays at both ends of a wireless link, which is known as massive MIMO. In this work the problem of reducing large overhead due to pilot...
In this paper, we investigate channel estimation methods in carrier aggregation (CA) orthogonal frequency division multiplexing (OFDM) systems. Carrier aggregation (CA) is one of the most distinct features of 4G that allows operators to deploy a system with larger bandwidth by aggregating several smaller contiguous or non-contiguous carriers. By taking advantage of the channel correlation that presents...
I/Q imbalance (IQI) is one of the major front-end imperfections affecting the performance of communication systems. Due to frequency-dependent (FD) IQI, channel is elongated and is split into direct and image channels. We consider the problem of joint estimation of the channel and I/Q parameters for OFDM based systems. Time-domain estimation of the effective channel taps poses a question: what is...
Massive multiple-input multiple-output (MIMO) has been actively studied for next generation wireless systems since it can provide high data rate and an improved energy efficiency in multiuser systems using large antenna arrays at base stations (BSs). While massive MIMO has various advantages, its perfor- mance is known to be limited by pilot contamination. To mitigate the intercell interference resulting...
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