1,721,021 research outputs found
Optimal Threshold Evaluation for TORC Detector of MC-CDMA Systems in Fading Channel
No full textIn this paper we investigate the performance of a
multi carrier-code division multiple access (MC-CDMA) system,
adopting an adaptive threshold orthogonality restoring combining
(TORC) detection technique. The analytical framework
we developed allows to derive the value of the threshold that
optimizes the performance in terms of bit error probability
as a function of the number of subcarriers, the number of
active users and the signal-to-noise ratio. This opens the way to
an adaptive variation of the threshold following slow processes
variations. A not negligible performance improvement, very close
to the optimum, but more complex, minimum mean square error
(MMSE) technique is shown
Combined partial equalization for MC-CDMA wireless systems
No full textWe analyze a combined equalization technique for multi carrier-code division multiple access (MC-CDMA) systems which consists in performing both pre-equalization at the trans- mitter and post-equalization at the receiver. In particular, a parametric partial equalization (PE) technique is considered at both sides, and we derive a generalized analytical framework to evaluate the bit error probability (BEP) and choose the optimal PE parameters which minimizes the BEP depending on system parameters
A distributed virtual traffic light algorithm exploiting short range V2V communications
No full textThe correct and prompt definition of priorities at intersections is one of the key issues for vehicular safety and efficient traffic management. Traffic lights currently control only a limited number of intersections and increasing their number is clearly infeasible due to the high costs of deployment and maintenance. A new solution will be possible in a near future, when vehicles will be equipped with wireless technologies. Their capability of communicating and coordinating to each other will create the conditions for the implementation of a virtual traffic light (VTL) architecture, where priorities are autonomously defined by the involved vehicles. With this scenario in mind, we describe a novel VTL algorithm aiming at defining the priorities of the intersections in a distributed and controlled way. Besides the algorithm description, the main related issues are thoroughly discussed. In addition, a real implementation is detailed and the validation of the algorithm is provided. The testbed, based on the IEEE 802.11p short range wireless technology, has been reproduced in a controlled laboratory environment and in a field trial with equipped vehicles
An OFDMA-Based MAC Protocol for Next-Generation VANETs
No full textVehicular ad hoc networks (VANETs) enable higher safety, enhanced mobility management, and new infotainment services. Currently, the foreseen standard at the medium access control (MAC) layer for VANETs is IEEE 802.11p, which is based on carrier sense multiple access with collision avoidance (CSMA/CA). However, under heavy traffic conditions, CSMA/CA suffers from a high collision probability, particularly in the presence of hidden terminals. Furthermore, the adoption of the request-to-send/clear-to-send (RTS/CTS) mechanism is not effective when a high data rate is required. If high-throughput services are addressed, a new MAC protocol should, thus, be designed. To this aim, in this paper, we propose a new protocol, which is denoted as the orthogonal frequency-division multiple-access (OFDMA)-based MAC protocol for VANETs (OBV), and we compare it with other MAC protocols taken as benchmarks. To verify the feasibility and the performance of the proposed algorithm, we first propose an analytical model in a simplified scenario. Then, we develop exhaustive simulations in realistic scenarios, considering both urban and highway environments. Results show that OBV outperforms all reference protocols, even doubling their throughput under heavy-load network conditions
Optimizing the Resource Allocation of Periodic Messages with Different Sizes in LTE-V2V
Full text linkRecently, 3GPP has added new features to long term evolution (LTE) that allow vehicles to communicate directly with each other and with surrounding objects. These short-range communications will play a key role in the so-called cellular vehicle-to-anything (C-V2X). As a particular service, which will be the basis of most applications for automated and connected cars, each vehicle will periodically broadcast information on its identity, status, and movements through short-range vehicle-to-vehicle (V2V) communications. Given the importance of this service, great attention has been given to the associated resource allocation procedures and the number of vehicles that can be simultaneously communicating in the network. However, little attention has been paid to handling messages of different sizes, which is actually foreseen in practice in order to transmit static information with a reduced periodicity. With this in mind, we evaluate the number of vehicles that can be allocated when parameters are optimized for messages of different sizes. This objective is pursued taking into account the numerous constraints imposed by the standard, through the formalization and solution of a combinatorial optimization problem. Example results, based on 3GPP indications, show that, with respect to the optimization of the allocation based on the larger packets, it is possible to obtain an increase that varies between 10% and 30%, depending on the conditions, with peaks above 150% in specific cases
Performance Improvement through Diversity Reception for Bluetooth on the Presence of Interference
No full textIn this work, we propose an analytical framework to derive the performance of Bluetooth (BT) in the presence of an IEEE802.11g interferer. In particular, aiming at improving the performance of BT in the presence of interference still maintaining low the complexity, we propose a selection diversity scheme at the receiver side of the BT system and we exploit the spatial diversity to improve the coexistence between different systems sharing resources. We firstly analytically derive the BT performance in terms of mean block error probability and mean packet error probability averaged over Rayleigh fading, then we extend the analysis to the evaluation of the packet error outage, an important figure of merit when real time scenarios are considered. We show that a not negligible improvement for the coexistence issue of the involved systems can be achieved
A survey on the roadmap to mandate on board connectivity and enable V2V-based vehicular sensor networks
Full text linkVehicles will soon be connected and will be interacting directly with each other and with the road infrastructure, bringing substantial benefits in terms of safety and traffic efficiency. The past decade has seen the development of different wireless access technologies for vehicle-to-everything (V2X) communications and an extensive set of related use cases have been drafted, each with its own requirements. In this paper, focusing on short-range communications, we analyze the technical and economic motivations that are driving the development of new road users’ connectivity, discussing the international intentions to mandate on board devices for V2X communication. We also go in depth with the enabling wireless access technologies, from IEEE 802.11p to short-range Cellular-V2X and other complementary technologies, such as visible light communication (VLC) and millimeterWaves, up to hybrid communication and 5G. We conclude our survey with some performance comparison in urban realistic scenarios, underlying that the choice of the future enabling technology is not so easy to predict and mostly depends on mandatory laws at the international level
Relay selection analysis for an opportunistic two-hop multi-user system in a poisson field of nodes
No full textIn this paper, we consider a multi-user scenario where an arbitrary number of sources transmit their messages to the intended destinations by means of relays in a decodeand-forward two-hop mechanism. To minimize the interference generated in the scenario, two opportunistic relay selection mechanisms are proposed and investigated. The performance of the two selection mechanisms is analytically evaluated, in terms of outage probability and average achievable rate, under the assumption that relay nodes are distributed according to a Poisson point process. Asymptotical analysis is also presented for infinite node density. Numerical results show that the selection of the relays has a significant impact on the amount of interference generated and a suitable choice can improve the overall performance
Performance analysis of V2v beaconing using LTE in direct mode with full duplex radios
No full textVehicles will soon be equipped with wireless communication systems enabling a variety of new services. At the basis of each service is the transmission of beacon messages that advertise the vehicle's presence. In this letter, we investigate long term evolution (LTE) as the enabling technology for vehicle to vehicle (V2V) beaconing by exploiting: 1) the direct device to device (D2D) communication provided by Release 12 of LTE; and 2) the full duplex (FD) radio, which allows a wireless device to transmit and receive at the same time. Furthermore, we introduce a novel analytical framework to evaluate the resource occupation of the beaconing service in LTE and compare the results with those obtained using LTE for vehicle to infrastructure (V2I) communications
On Bluetooth Performance with Diversity Reception in Fading Channels
No full textThis paper investigates the impact of diversity reception techniques on the performance of Bluetooth (BT) packet transmission in fading channels. We firstly derive a tight parametric exponential approximation for the bit error probability in additive white Gaussian noise depending on GFSK modulation parameters according to the BT standard. Then, from this expression we derive the mean block error probability (BLEP) for DH packets transmission in Rayleigh fading channel by adopting different diversity reception techniques, such as selection diversity and maximal ratio combining (MRC). In particular, the impact of the diversity order and combining techniques on the BLEP is shown. For the MRC technique, we also obtain a tight bound on the BLEP. Furthermore, we extend the results for MRC to Nakagami-m fading and we obtain the parameters of exponential approximation for a general GFSK modulation, although out of BT standard, showing their impact on both the performance and spectrum
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