1,721,111 research outputs found
Localization of a Nano-transmitter in a Diffusive MC System with Multiple Fully-absorbing Receivers
No full textThis paper presents new results about localization of a pointwise transmitter in a molecular communication (MC) diffusive channel by means of a spherical array whose elements are fully-absorbing (FA) receivers. The performance of two different spherical arrays is analyzed to estimate the position of the transmitter that differ in the configuration of the FA receivers on their surface. The proposed localization method relies on a model that has been recently developed to predict the temporal asymptotic cumulative number of molecules absorbed by each of the FA receivers. The approach first estimates the distances between the transmitter and the FA receivers and then use them in a multilateration technique. One of the most promising applications of localization in telemedicine is targeted-drug delivery, which is realized by means of nano-robots. Numerical results are used to demonstrate the accuracy of the proposed method
Reinforcement learning aided uav base station location optimization for rate maximization
Full text linkThe application of unmanned aerial vehicles (UAV) as base station (BS) is gaining popularity. In this paper, we consider maximization of the overall data rate by intelligent deployment of UAV BS in the downlink of a cellular system. We investigate a reinforcement learning (RL)-aided approach to optimize the position of flying BSs mounted on board UAVs to support a macro BS (MBS). We propose an algorithm to avoid collision between multiple UAVs undergoing exploratory movements and to restrict UAV BSs movement within a predefined area. Q-learning technique is used to optimize UAV BS position, where the reward is equal to sum of user equipment (UE) data rates. We consider a framework where the UAV BSs carry out exploratory movements in the beginning and exploitary movements in later stages to maximize the overall data rate. Our results show that a cellular system with three UAV BSs and one MBS serving 72 UE reaches 69.2% of the best possible data rate, which is identified by brute force search. Finally, the RL algorithm is compared with a K-means algorithm to study the need of accurate UE locations. Our results show that the RL algorithm outperforms the K-means clustering algorithm when the measure of imperfection is higher. The proposed algorithm can be made use of by a practical MBS–UAV BSs–UEs system to provide protection to UAV BSs while maximizing data rate
Design of DGT-based linear and non-linear equalizers for GFDM transmission
Full text linkThis paper exploits the parallelism between Discrete Gabor Transform (DGT) and Generalized Frequency-Division Multiplexing (GFDM) that exists when the synthesis function, i.e. the pulse shaping filter, and the analysis function, i.e. the receiving filter, satisfy the Wexler–Raz identity. Choosing functions that satisfy the Wexler–Raz condition allows optimal symbol-by-symbol detection for a DGT-based GFDM receiver in case of transmission over an additive white Gaussian noise channel. However, multipath fading is the major problem of the wireless communication channel, hence, when transmission takes place over frequency selective channel, symbol-by-symbol detection is no longer optimal due to interference generated among the transmitted symbols. In this work, we deal with the design of linear and non-linear receivers for DGT-based GFDM transmission over a frequency selective channel that allows a good trade-off between complexity and performance. Different equalization schemes to mitigate distortions, such as Maximum Likelihood, Zero-Forcing and Minimum Mean-Squared Error, are developed and analyzed. Monte Carlo simulations are used to evaluate the error rate performance achieved with the considered design. A comparison is done with other works in the literature
Confidence Interval of Peak-Based Distance Estimation in Diffusive Molecular Communication
No full textMolecular Communication (MC) is a bio-inspired communication paradigm, where chemical signals (molecules) carry information. Using molecules as information carriers, rather than electrons or electromagnetic waves, allows communication in environments not considered before, as inside the human body or between nano-machines. This form of communication is particularly interesting due to its simplicity and the low energy cost with respect to the other communication systems.In this article, a specific aspect, which has been not given much attention in literature yet, is examined. Starting from the impulse response estimated for an MC diffusive channel between a point transmitter and a fully absorbing receiver in a three-dimensional space, the confidence interval of the distance from transmitter to receiver is estimated, based on the peak value of the channel impulse response. The analysis adopts the well-known Clopper-Pearson method for confidence interval evaluation
Characterization of the indoor-to-outdoor wireless channel in air-to-ground communication systems
Full text linkWireless communication between User Terminals (UTs) inside a building and an outdoor base station mounted onboard an unmanned aerial vehicle (UAV) is receiving a higher interest in emergency management scenarios and where users require on demand high throughput services. In such applications, a fundamental aspect is the thorough characterization of the propagation environment through parameters such as the UTUAV distance and the number of walls and floors crossed. In this paper, we characterize the indoor-to-outdoor wireless channel by using a commercial ray-tracing software. The reference scenario is a four-floor building. The UTs are uniformly distributed within each floor and two UAV positions are considered nearby the building. As a main contribution, we present numerical results in terms of path loss against the UT-UAV distance. The dependence of the path loss on the number of floors between the UT and the UAV is highlighted as well. Finally, the ray-tracing results are compared with those predicted by a few available propagation models
Asymptotic MIMO Channel Model for Diffusive MC With Fully-Absorbing Receivers
No full textThis letter introduces an analytical model that gives the expected asymptotic cumulative number of molecules absorbed by each spherical receiver in a diffusive multiple-input multiple-output (MIMO) molecular communication (MC) system with pointwise transmitters. The reciprocal effect among the fully absorbing (FA) receivers is taken into account by using the recently introduced concept of fictitious pointwise negative source of molecules. An agreement is shown between the proposed asymptotic model and the numerical solution of the exact analytical one from the literature describing the interaction among the receivers, which is computed for a sufficient long time
What Is the Trait d’Union between Retroactivity and Molecular Communication Performance Limits?
Full text linkInformation exchange is a critical process in all communication systems, including biological ones. Retroactivity describes the load that downstream modules apply to their upstream systems in biological circuits. The motivation behind this work is that of integrating retroactivity, a concept proper of biochemical circuits, with the metrics defined in Information Theory and Digital Communications. This paper focuses on studying the impact of retroactivity on different biological signaling system models, which present analogies with well-known telecommunication systems. The mathematical analysis is performed both in the high and low molecular counts regime, by mean of the Chemical Master Equation and the Linear Noise Approximation, respectively. The main goal of this work is to provide analytical tools to maximize the reliable information exchange across different biomolecular circuit models. Results highlight how, in general, retroactivity harms communication performance. This negative effect can be mitigated by adding to the signaling circuit an independent upstream system that connects with the same pool of downstream circuits
A machine learning-based design of PRACH receiver in 5G
Full text linkThe physical random access channel (PRACH) in the uplink of cellular systems is used for the initial access requests from users. In fifth generation (5G) systems three different types of services are available, which are massive machine-type communication, enhanced mobile broadband communication, and ultra-reliable low-latency communication. Considering the tight requirements in terms of latency, a robust design of PRACH receiver is one of the priorities. In this paper we first explore the simple extension of a technique proposed for fourth generation (4G) systems to 5G. Then we propose the application of machine learning techniques to make the PRACH receiver more robust to false peaks, which are responsible of performance degradation in the extension of the 4G technique to 5G. Monte Carlo simulations are used to evaluate and compare the performance of the proposed algorithms
Modified Inverse Source Coding for Diffusion Based Molecular Communication System
Full text linkIn this paper we prove that Inter-Symbol Interference (ISI) and Bit Error Rate (BER) of a Diffusion Based Molecular Communication (DBMC) system depend on the a-priori probability of the transmitted data by deriving lower and upper bounds for the number of received molecules. We also compute the optimal value of a-priori probability for which ISI and BER are minimized. A source coding technique, called Modified Inverse Source Coding (MISC), is proposed that allows to control the a-priori probability of the transmitted data. The results show that the MISC-DBMC system not only provides a better BER performance compared to an uncoded one but also improves the range of communication
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