523 research outputs found
Performance trade-offs of different rake receivers
No full textIn this paper we determine the effects of different diversity schemes on the behavior of a direct-sequence spread spectrum Rake receiver which operates with random spreading sequences, in a multipath channel with arbitrary power delay profile. Two different receiver architectures, the former employing the L instantaneously strongest paths out of the Nr resolved ones, and the latter simply the L first paths out of the received Nr, are confronted in terms of symbol error probability, when an M-level PSK system is assumed. The analytical approach devised for assessing such comparison gives the symbol error probability in terms of simple elementary integrals, and immediately evidences the influence on system behavior of the number of resolved paths, bandwidth occupancy of the signal and power delay profile, with a remarkably moderate computational effort
A comparison between outage probability evaluations in microcellular systems
No full textThe effects of cochannel interference in a UHF microcellular system operating in a Ricean/Rayleigh fading environment are investigated: the aim is to prove in the microcell domain the validity of a simplified analytical methodology, already successfully applied in traditional cellular structures, which allows to evaluate almost effortlessly the outage probability, i.e., the probability of failing to achieve a satisfying signalto-interference ratio. The results obtained confirm the validity of this new approach also in the microcell environment, for a wide range of the parameters involved in the system, fading and propagation model description
MoReV2X - A New Radio Vehicular Communication Module for ns-3
No full textThe Third Generation Partnership Project (3GPP) recently released the 5G New Radio (NR) Vehicle-to-Everything (V2X) standard. NR-V2X is expected to support a large set of enhanced V2X applications, characterized by stringent requirements in terms of latency, reliability and data rate. The use of simulations plays a crucial role in the preliminary assessment of NR-V2X achievable performance, providing valuable insights on the strengths and limits of the new solution. This work introduces MoReV2X, an open-source ns-3 module for the simulation of NR-V2X communications. The development of MoReV2X adheres to 3GPP specifications, includes various traffic models, features an accurate implementation of the NR propagation channel between vehicles and allows to determine a thorough set of Key Performance Indicators (KPIs). A first set of exemplary results is reported to testify the proper functioning of the module. Moreover, the results reveal the impact that different subcarrier spacings have on system performance, when periodic and aperiodic traffic sources are considered
Impact of fast fading compensations on mobile radio system performance
No full textThis paper explores what benefits can result from the compensation of both log-normal shadowing and Rayleigh/Rice-fading fluctuations in a mobile radio environment. The focus is on those power-control policies that exclusively make use of local power-level measurements in order to improve the performance, measured in terms of signal-to-cochannel interference ratio, of time-division multiple-access cellular radio systems; the aim is in fact to demonstrate under what circumstances the power compensation can be advantageously exploited. The corresponding analysis accounts for the errors due to the delay constraints that time-division and transmission techniques such as interleaving inevitably force onto the control loops. The numerical results quantitatively outline the maximum benefits on system performance that derive from the introduction of fast fading compensation for the class of power-control policies investigated in this paper. The remarkable influence of delay errors on the effectiveness of the fast fading control procedures are clearly revealed
A Statistical Characterization of the Actual Cooperative Perception Messages and a Generative Model to Reproduce Them
No full textThis paper provides two novel contributions to
vehicular cooperative perception. Firstly, it puts forth an approach to generate the actual perception messages broadcasted
by connected autonomous vehicles. Relying on data gathered
by autonomous vehicles and originally collected for computer
vision purposes, it produces perception messages in accordance
with the standard ETSI rules. The statistical properties of the
messages are determined, showing that their size is remarkably
affected by the driving scenario and the policy adopted to
discern when an object is seen by the vehicle, and to a lesser
extent by the selection of the message generation frequency.
Secondly, the paper proposes a generative model to synthetically
replicate the sequences of perception messages. The ability of
the model to successfully capture the characteristics and the
temporal correlation of the real data is demonstrated in a
reference scenario. The model adoption is promising in largescale numerical simulations, where the perception messages of
many vehicles have to be faithfully reproduced
Performance of a 3rd Generation Radio Link Control Protocol on a Multicarrier DS-CDMA System
No full textThis work investigates the behavior of a 3 rd Generation Radio Link Control Protocol on the forward link of a Multicarrier DS-CDMA architecture that employs Walsh and Quasi-Orthogonal channelization codes. Protocol performance is analytically assessed, determining the average delay suffered by a data unit transferred over the radio channel. For alternative allocation policies of Walsh and Quasi-Orthogonal codes, the effects on throughput of different transmission qualities and size of protocol data units are evaluated. system design
Voice and data services in multicode and variable spreading factor DS-CDMA systems
No full textThis paper analyzes the uplink capacity of multicode and variable spreading factor DS-CDMA cellular systems which accommodate users with different transmission rate requirements. It takes into account imperfect power control on slow signal fluctuations due to shadowing, the presence of Rayleigh fading and a random location of the users. The circumstance where the portable transmits to the nearest base station is examined; when shadowing only is present, the possibility that the user chooses the least interfered among Nc nearest base stations is also considered. System capacity is determined analytically, employing two distinct approximations featuring low computational costs, as well as by simulation. The latter approach allows to compare the accuracy of the analytical approximations for a wide range of system parameters
On the assignment of Walsh and quasi-orthogonal codes in a multicarrier DS-CDMA system with multiple classes of users
No full textSeveral code allocation policies, suitable for the forward link of a Multicarrier DS-CDMA mobile radio system that employs Walsh and quasi-orthogonal sequences, were presented. Their effect on system performance was evaluated in the presence of a single class of users. The performance achieved by two classes of subscribers was assessed in a frequency selective fading environment
Multicarrier DS-CDMA performance with different assignment strategies of quasi-orthogonal codes
No full textAlternative code assignment policies for the forward link of a multicarrier DS-CDMA system employing the recently proposed quasi-orthogonal sequences are put forth in this paper. It is demonstrated how different allocation strategies of quasi-orthogonal codes alter the interference level suffered by active units; it is also shown how to shape the rate of interference growth as a function of the number of active users within the reference cell, by implementing some specific code allocation patterns. The performance, in terms of average bit error probability, achieved by various schemes is assessed in a frequency selective fading environment, and the advantages of different solutions highlighted. ©2002 IEEE
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