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A wireless relay node employing Wireless Physical Layer Network Coding (WPLNC) must use a specific mapping in order to combine incoming signals. This mapping, however, cannot be selected arbitrarily. Together with the signals from the other network relays, it has to allow the destinations to be able to recover the source data from the available observations. Moreover the mapping should optimize a...
We consider overloaded (non-orthogonal) code division multiple access multiuser wireless communication systems with many transmitting users and one central aggregation node, a typical scenario in e.g. machine-to-machine communications. The task of the central node is to detect the set of active devices and separate their data streams, whose number at any time instance is relatively small compared...
The realtime identification of missing items, e.g., valuables or confidential documents in shops and warehouses, is one of the most important system. Although many RFID-based schemes that quickly identify missing tag-attached items are proposed, most of the schemes overlooks the possibility of the internal crime. If a person controls an untrusted reader, he/she can freely forge responses from tags...
Wireless energy harvesting (WEH) provides an exciting way to supply energy for relay nodes to forward information for the source-destination pairs. In this paper, we investigate the problem on how the relay node dynamically adjusts the power splitting ratio of information transmission (IT) and energy harvesting (EH) in order to achieve the optimal outage performance. According to the knowledge of...
This paper studies the eigenvalue decomposition (EVD) based uplink channel estimation in multi-cell massive multi-input multi-output (MIMO) networks. The performance of the conventional EVD-based channel estimators is limited by the interference from other users in the network due to finite number of antennas and finite transmit samples. We propose an iterative optimization procedure with multiple...
Millimeter wave (mmWave) technologies can enable current mobile communication systems to achieve higher data rates. However, wireless channels at mmWave frequencies experience higher isotropic path loss. Therefore, employing a suitable beamforming algorithm is an indispensable element of any mmWave system. Traditional multiple-input multiple-output (MIMO) systems employ digital beamforming where each...
We consider user activity estimation for on-off random access in multi-base station systems. With on-off random access, each user, at a fixed slot, transmits its unique codeword (and is hence active) with probability p, and is heard by all base stations in its vicinity; the goal for each base station is then to determine which of the users in its coverage region are active. This problem models various...
In this paper, we propose a full-duplex physical-layer network coding (FD-PLNC) scheme for reciprocal asymmetric frequency-selective multipath channels using orthogonal frequency-division multiplexing (OFDM) and denoise and forward (DNF) relaying. We consider a network scenario of two-way relay channels (FD-TWRCS) with two source nodes, A and B, intending to exchange information with the aid of a...
We study the problem of amplify-and-forward relaying in a hybrid satellite-terrestrial communication system with imperfect channel gains. Signals are received by masked destination earth station (ES) with the help of a relaying ES, situated at the ground with good line-of-sight. No direct transmission is possible from the satellite to the destination ES. The satellite-relay ES link is assumed to be...
We investigate the information-theoretic throughout achievable on a fading communication link when the receiver is equipped with one-bit analog-to-digital converters (ADCs). The analysis is conducted for the setting where neither the transmitter nor the receiver have a priori information on the realization of the fading channels. This means that channel-state information needs to be acquired at the...
This paper investigates the applicability of generalized frequency division multiplexing (GFDM) for an uplink scenario where several users are not perfectly synchronized, as it appears in wireless sensor networks (WSN). We compare the performance in terms of inter-user interference (IUI) caused by time and frequency misalignments between users, where the physical layer is realized with GFDM and OFDM...
In this paper, a sectorized multi-cell massive multiple-input multiple-output (MIMO) system is considered with a spatially correlated channel model. Since sum-throughput per cell is an important index for evaluating a multi-cell system, we derive the ergodic achievable uplink sum-throughput per cell of the sectorized system and give the deterministic approximation of it based on the large random matrix...
In the future super dense wireless networks, millimeter-wave (mmWave) communications systems have great prospects, mainly due to the huge bandwidths and the directional transmissions. However, phase noise is significant due to the high oscillation frequency, which affects channel estimation and deteriorates the bit-error-rate (BER) performance. This paper emphasizes that phase noise may be estimated...
Recently, much attention has been paid to the green design of wireless communication systems using energy efficiency (EE) metrics that should capture all energy consumption sources to deliver the required data. In this paper, we formulate an accurate EE metric for cooperative two-hop systems that use the amplify-and-forward relaying scheme. Different from the existing research that assumes the availability...
Pilot contamination is known to be one of the main impairments for massive MIMO multi-cell communications. Inspired by the concept of fractional frequency reuse and by recent contributions on pilot reutilization among non-adjacent cells, we propose a new pilot allocation scheme to mitigate this effect. The key idea is to allow users in neighboring cells that are closest to their base stations to reuse...
This paper considers the problem of coordinated multi-point transmission from transmitter devices that acquire noisy and partial channel state information (CSI) estimates from local feedback links. As cooperative multi-antenna transmission often relies on the availability of global channel estimates, we propose a novel decentralized algorithm that produces MMSEoptimal channel estimates on the basis...
For fast-moving vehicles, radio channels can be severely fast-fading. Under such circumstances, the performance of multi-carrier communication systems, such as OFDM-based ones, are often limited by the inter-carrier interference (ICI) caused by time variation of the channel within one transmit symbol. The conventional way to mitigate the effect of ICI is to increase the frequency spacing between neighboring...
In this paper, a location-based channel estimation algorithm is proposed for massive multi-input multi-output (MIMO) systems. By utilizing the property of the steering vector, a fast Fourier transform (FFT)-based post-processing is introduced after the conventional pilot-aided channel estimation. Under the condition that different users with the same pilot sequence have non-overlapping angle-of-arrivals...
Massive multiple input multiple output (MIMO) millimeter wave (MMW) communications allow for a compact implementation and efficient beamforming. In this paper we focus on the problem of estimating the massive MIMO channel in a code modulated path sharing multi-antenna (CPMA) architecture, when a limited number of radio frequency (RF) chains is available, and beamforming is performed through a combination...
In this paper, a cooperative channel estimation strategy is proposed in multi-cell large scale antenna systems (so-called “massive MIMO”). Based on time-shifted uplink pilot sequences, the strategy can alleviate the performance degradation caused by the pilot contamination. In addition, the truncated conjugate gradient trust region (TCGTR) algorithm is proposed to estimate the channel vectors. The...
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