1,721,028 research outputs found
On the Outage Capacity of the Massive MIMO Diversity Channel
Full text linkWe consider the massive Multiple Input Multiple Output (MIMO) diversity
channel affected by independent and identically distributed Rayleigh fading,
with linear processing at both transmitter and receiver sides, and analyze the
outage capacity for large number of antennas. We first discuss the classical
Single Input Multiple Output (SIMO) diversity channel that uses Maximal Ratio
Combining (MRC) or Selection Combining (SC). For MRC, a numerical computation
and a Gaussian Approximation (GA) are considered, whereas for SC an exact
evaluation is possible. The analysis is then straightforwardly extended to the
Multiple Input Single Output (MISO) system that uses Maximal Ratio Transmission
(MRT) or transmit antenna selection. The general Multiple Input Multiple Output
(MIMO) system that pursues full diversity is finally considered, with both
optimal linear processing and simple antenna selection at both transmitter and
receiver. If the number of antennas is sufficiently large on at least one side,
the outage capacity of each considered diversity channel approaches that of a
suitable reference Additive White Gaussian Noise (AWGN) channel with properly
defined Signal-to-Noise Ratio (SNR), which provides a performance benchmark.
This conclusion is valid for large but realistic number of antennas compatible
with the assumption of independent fading
Improved UWB TDoA-based Positioning using a Single Hotspot for Industrial IoT Applications
Full text linkThe goal of this paper is to investigate Ultra WideBand (UWB) localization with Time Difference of Arrival (TDoA) processing at the anchors. We consider scenarios where the anchors are placed very close to each other and the target to be localized is around the group of anchors. All target-anchor communications are assumed to be in Line-Of-Sight (LOS). Since our analysis shows that symmetries in anchors' placement, with respect to the target position, degrade the positioning accuracy of standard algorithms, we propose to use a Subset Selection (SS) strategy, where position estimates obtained with properly selected subsets of asymmetric anchors are fused together to get the final localization output. Our results show improved localization accuracy with respect to the use of all anchors, especially in estimating the angle of arrival. Finally, we analyze the impact of an inaccurate time synchronization among the anchors, deriving guidelines for hardware implementation
Heuristic Design of Feedback Active Noise Control for Automotive Applications
No full textIn this paper, a performance analysis of FeedBack (FB) Active Noise Control (ANC) systems for automotive applications is presented. Noise cancellation is obtained from a fixed controller, heuristically designed using concepts from control theory. An experimental setup, representative of a headrest of a car seat with loudspeaker-microphone distance on the order of a few centimeters, has been developed to limit the system delay. The experimental band-limited noise source has been obtained from an idling car. Our results show that the proposed system guarantees appreciable peak noise cancellation and simultaneously avoids noise amplification outside the band of interest
Low-Complexity Channel Estimation in OFDM MU-MIMO Next Generation Cellular Networks
No full textWe consider downlink communications between a Base Station (BS) and various mobile stations, equipped with multiple antennas, based on Orthogonal Frequency Division Multiplexing (OFDM). Transmission is compliant with the Long Term Evolution (LTE) standard operating in Frequency Division Duplex (FDD) mode. Since ideal feedback of channel state information to the BS may be cumbersome, we consider two suboptimal channel estimation algorithms, denoted as Resource Block (RB) and Resource Block Group (RBG). Both approaches approximate the channel as constant over multiples of the fundamental LTE block, known as Physical Resource Block (PRB). Our results show that RB and RBG incur a limited performance loss, yet guaranteeing significant saving in the amount of feedback information
UWB TDoA-based Positioning Using a Single Hotspot with Multiple Anchors
No full textIn this paper, we address target positioning in scenarios where the reference nodes, denoted as anchors, are not distributed at the perimeter of the area where the target is, but are concentrated in a very small region and target is outside this region. This scenario may be meaningful in smart building applications, where anchor nodes cannot be distributed and cabled in the monitored area. On the other hand, anchors may be installed on a single hotspot to be placed at the center of the environment of interest. In this case, the target has to be localized outside the polytope identified by the anchors. To this end, we investigate Ultra WideBand (UWB)-based target positioning with Time Difference of Arrival (TDoA) processing at the anchors. A comparative analysis between geometric and Particle Swarm Optimization (PSO) algorithms is carried out. Our results show accurate angle of arrival estimation accuracy. Moreover, while PSO guarantees a better performance, in terms of average position estimation error, the “dispersion” of position estimation (i.e., the standard deviation of the position error) is higher than in the case of geometric algorithms
Trustworthy task allocation in IoT: a cognitive game-theoretical use case
No full textThis Chapter analyzes how malicious attacks affect the performance of a heterogeneous Internet of Things (IoT) system where cognitive devices collaborate to negotiate task assignments. In the reference scenario, the involved devices create clusters, each managed by a Cluster Head (CH). Whenever a task is required, the CH triggers spectrum sensing to detect spectrum holes that can be opportunistically exploited by the nodes of the cluster for task allocation. In this scenario, not all the nodes are Honest Nodes (HN). Indeed, Malicious Nodes (MNs) may hinder the process and try to disrupt it by providing tampered data, which would lead to a higher likelihood that the spectrum sensing is not performed correctly. When the spectrum is considered free, the cluster nodes negotiate to execute the required task by means of an auction-based game theory approach. The negotiation takes into account two factors: the reward gained from contributing to the execution of the task, which is provided to the node that wins the competition, and the energy cost to perform the task. Specifically, the Chapter investigates how MNs affect the reward aspect when they try to gain maximum control over the task and potentially launch a Denial of Service (DoS) attack. Extensive simulations are run to assess the effect of the key system parameters on the overall performance and provide recommendations for future research
Zigbee sensor networks with data fusion
No full textIn this paper, we propose a simulation-based analysis of the impact of data fusion mechanisms in a Zigbee sensor network used to monitor a spatially constant binary phenomenon. The performance indicators of interest are both physical layer-oriented (Bit Error Rate, BER) and networking- oriented (throughput, delay, and aggregate throughput). The considered topologies encompass both the absence and the presence of clustering. In the first class of scenarios, we analyze the impact, on the system performance, of the number of transmitting sensors, the Signal-to-Noise Ratio (SNR) at the sensors, and the presence of ACKnowledgment (ACK) messages. In the second class of scenarios, instead, we analyze the BER performance, in the presence of uniform and non-uniform clustering configurations. Data fusion is considered at the Access Point (AP) and, in clustered configurations, also at the clusterheads, which act as intermediate Fusion Centers (FCs). To the best of our knowledge, we are the first to characterize a Zigbee sensor network from a joint physical layer/networking perspective. Moreover, the proposed simulation results confirm recently obtained theoretical results
Pragmatic code-aided phase synchronization in iterative multi-sample receivers
No full textIn this paper, we consider communications impaired by phase noise and we propose an iterative multi-sample receiver, where the received signal is sampled with more than one sample per symbol interval. The approach is pragmatic in the sense that demodulation/decoding is performed separately from synchronization and relies on “off-the-shelf” subblocks. In particular, we extend a recently proposed Maximum A-posteriori Probability (MAP)-based algorithm for phase synchronization by exploiting oversampling at the receiver. Our simulation results show an improved performance with respect to a “classical” receiver, where phase synchronization relies on one sample per symbol interval only, for high phase noise scenarios
Information rate analysis of the oversampled phase-noise channel
No full textIn this paper, we analyze the information rate of a phase-noise discrete-time channel obtained by sampling the continuous-time channel. In particular, we assume that more than one sample per data symbol may be available at the receiver, so that this channel is referred to as "oversampled." This work extends previous literature work by taking into account the presence of a bandlimited shaping pulse at the transmitter with time support not limited to the symbol period, possibly causing inter-symbol interference. Our results show that for sufficiently large signal-to-noise ratio (SNR) it is possible to recover the performance degradation caused by phase noise, also for quite large values of the phase noise intensity
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