Unsaturated Throughput Analysis of IEEE 802.11 in Presence of Non Ideal Transmission Channel and Capture Effects

In this paper, we provide a throughput analysis of the IEEE 802.11 protocol at the data link layer in non-saturated traffic conditions taking into account the impact of both transmission channel and capture effects in Rayleigh fading environment. The impact of both non-ideal channel and capture become important in terms of the actual observed throughput in typical network conditions whereby traffic is mainly unsaturated, especially in an environment of high interference. We extend the multi-dimensional Markovian state transition model characterizing the behavior at the MAC layer by including transmission states that account for packet transmission failures due to errors caused by propagation through the channel, along with a state characterizing the system when there are no packets to be transmitted in the buffer of a station. Finally, we derive a linear model of the throughput along with its interval of validity. Simulation results closely match the theoretical derivations confirming the effectiveness of the proposed model.Comment: To appear on IEEE Transactions on Wireless Communications, 200

Saturation Throughput Analysis of IEEE 802.11 in Presence of Non Ideal Transmission Channel and Capture Effects

In this paper, we provide a saturation throughput analysis of the IEEE 802.11 protocol at the data link layer by including the impact of both transmission channel and capture effects in Rayleigh fading environment. Impacts of both non-ideal channel and capture effects, specially in an environment of high interference, become important in terms of the actual observed throughput. As far as the 4-way handshaking mechanism is concerned, we extend the multi-dimensional Markovian state transition model characterizing the behavior at the MAC layer by including transmission states that account for packet transmission failures due to errors caused by propagation through the channel. This way, any channel model characterizing the physical transmission medium can be accommodated, including AWGN and fading channels. We also extend the Markov model in order to consider the behavior of the contention window when employing the basic 2-way handshaking mechanism. Under the usual assumptions regarding the traffic generated per node and independence of packet collisions, we solve for the stationary probabilities of the Markov chain and develop expressions for the saturation throughput as a function of the number of terminals, packet sizes, raw channel error rates, capture probability, and other key system parameters. The theoretical derivations are then compared to simulation results confirming the effectiveness of the proposed models.Comment: To appear on IEEE Transactions on Communications, 200

Multirate 5G Downlink Performance Comparison for f-OFDM and w-OFDM Schemes with Different Numerologies

One of the main open problems for next generation wireless networks, is to find the new OFDM-based waveform to be used in 5G. The new modulation scheme must primarily be able to achieve higher spectral efficiency than its predecessor. The main 3GPP's candidate is a new version of OFDM, called Filtered Orthogonal Frequency-Division Multiplexing (f-OFDM), which is similar to OFDM but with additional filtering in order to reduce Out-Of-Band (OOB) emissions and to obtain a better spectral-localization. Another option is windowed-OFDM (w-OFDM), which is basically a classical OFDM scheme where each symbol is windowed and overlapped in the time domain. In this paper we compare classic OFDM signals using Cyclic Prefix (CP-OFDM) with f-OFDM and w-OFDM, each one with multiple parametric options and numerologies. A multirate transmitter simultaneously operating with multiple numerologies is considered, where the transmitted sub-bands must be up-sampled and interpolated in order to generate the composite numerical signal fed to the Digital to Analog Converter (DAC). Finally, we discuss advantages and disadvantages of the various schemes.Comment: Paper accepted for ISNCC 201

IMPROVED RECEIVER FOR WIRELESS COMMUNICATIONS NETWORKS

An iterative receiver is proposed for receiving in a cell a signal (A) and for providing information carried on said signal (A) by the execution of at least one processing iteration. The receiver comprises: an estimate assembly for receiving the signal (A) and providing, at each one of said processing iterations, a respective information estimate ; a regeneration assembly for receiving, at each processing iteration, said information estimate provided by the estimate assembly at that iteration, and for providing a regenerated signal (B) therefore based on said information estimate and on attenuation of radio channels over which the signal (A) has been transmitted; an interference estimate unit for providing, at each iteration, an interference estimate (C) based on the signal (A) and the regenerated signal (B), the estimate assembly providing, starting from a second processing iteration of said processing iterations, said information estimate based on said interference estimate; and an extraction unit for extracting said information from said information estimate

Advanced Communication Techniques and Applications for High-Altitude Platforms

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A study on multi-RIS for multi-user distributed MIMO systems

This paper presents a preliminary analysis on the impact of Reconfigurable Intelligent Surfaces (RISs) for the realization of multi-user Distributed multiple input multiple output (DMIMO) systems, where the distributed units are actually RISs. Assuming no direct link between the multi-antenna Access Point (AP) and the users, we design the joint transmit beamforming from the AP to the set of RISs associated to each user, performed via RIS phase shift shaping. In order to comply with the semipassive nature of RISs, the phase shifts are computed via a Genetic Algorithm (GA), where the optimization is based on the Signal-to-Leakage-and-Noise-Ratio (SLNR) precoding scheme. Numerical results confirm that this GA implementation significantly outperforms the common Maximum Ratio Beamforming (MRB) approach in terms of interference suppression and sumrate, but at the price of a significant increase in computational complexity. Our solution justify the interest of a multi-RIS system for spatial multiplexing, and opens to several further research directions

Simulation and Complexity Analysis of Iterative Interference Cancellation Receivers for LTE/LTE-Advanced

The paper details the simulation of a single user MIMO receiver operating according to the 3GPP/LTE standard applying a Parallel or Successive Interference Cancellation (PIC/SIC) strategy to a multicarrier (OFDMA/SC-FDMA) scheme. The algorithm details are analyzed and the PIC and SIC cancellation strategies are simulated and compared on random MIMO selective fading channels, considering limited complexities. The best PIC and SIC schemes for a given limited complexity (8 turbo decoding iterations per codeword) are compared for different codeblock lengths and spatial correlation scenarios over an EPA channel model. The 2 cycles SIC scheme shows the best performance over the selected scenarios, offering gains over the non-iterative schemes (measured at BLER values of 0.1) ranging from 1 to 4 dB in the considered cases. Larger gains are obtained with higher spatial correlation and shorter codeblock lengths. Better overall performance are obtained with lower spatial correlation and longer codeblock lengths

Capacity Optimization of Channel Models for a Pragmatic QKD Protocol Based on Spatial Entanglement of Twin Beams in PDC

One of the key issues in QKD is the rather limited data rate at which the secret key can be generated. This paper explores the use of twin beams in a PDC process for imaging CCD devices whose photon counts in symmetric pixel positions can be used to generate secret keys. The fundamental reason is that the two beams are entangled in the photon number state and measurements of the correlation statistics should theoretically expose the presence of the eavesdropper. Via a binning approach the photon counts at Alice and Bob who each image one of the two beams, can be turned into discrete labels that represent elements of the raw key that needs further reconciliation and privacy amplification. Discrepancies between the photon counts can be modeled via a fictitious discrete memoryless channel. Furthermore, the use of multi-pixels images allows to create a number of parallel channels for generation of secret keys, thus significantly boosting the achievable key rate. This work explores the derivation of proper channel models for this application starting from measured data and the optimization of the secret key rate. Trade-offs between error probability and key rate are analyzed, with the final goal of maximizing the system Shannon capacity

ANALISI TEORICHE E PROVE SPERIMENTALI DI UN SISTEMA DIMONITORAGGIO DI FRANE CON EMISSIONE ACUSTICA

Viene illustrato un esperimento per valutare la fattibilità di un sistema di monitoraggio di frane in roccia tramite il rilevamento di emissioni acustiche e la individuazione della localizzazione spaziale delle sorgenti di emissione