Search results for "Packet loss"
showing 10 items of 24 documents
Impact of LoRa Imperfect Orthogonality: Analysis of Link-Level Performance
2018
In this letter, we focus on the evaluation of link-level performance of LoRa technology, in the usual network scenario with a central gateway and high-density deployment of end-devices. LoRa technology achieves wide coverage areas, low power consumption and robustness to interference thanks to a chirp spread-spectrum modulation, in which chirps modulated with different spreading factors (SFs) are quasi-orthogonal. We focus on the performance analysis of a single receiver in presence of collisions. First, we analyze LoRa modulation numerically and show that collisions between packets modulated with different SFs can indeed cause packet loss if the interference power received is strong enough…
LoRa Technology Demystified: From Link Behavior to Cell-Level Performance
2020
In this paper we study the capability of LoRa technology in rejecting different interfering LoRa signals and the impact on the cell capacity. First, we analyze experimentally the link-level performance of LoRa and show that collisions between packets modulated with the same Spreading Factor (SF) usually lead to channel captures, while different spreading factors can indeed cause packet loss if the interference power is strong enough. Second, we model the effect of such findings to quantify the achievable capacity in a typical LoRa cell: we show that high SFs, generally seen as more robust, can be severely affected by inter-SF interference and that different criteria for deciding SF allocati…
Testing the H.264 error-resilience on wireless ad-hoc networks
2004
The purpose of this paper is to provide a framework to tune and evaluate the performance of the H.264 codec in 802.11b wireless ad-hoc networks. The codec's error-resilience features are measured under stress conditions typical to these networks, and the most critical parameters are presented. We present solutions concerning the random packet loss problem and show how to quickly recover from packet loss bursts.
Enabling Retransmissions for Achieving Reliable Multicast Communications in WSNs
2016
To ensure end-to-end reliable multicast or broadcast transmissions in IEEE 802.15.4 based wireless sensor networks WSNs) is a challenging task since no retransmission and acknowledgment mechanisms are defined in such WSNs. In this paper, we propose three retransmission enabled multicast transmission schemes in order to achieve reliable packet transmissions in such networks. Different from the legacy CSMA/CA principle, these schemes allow a sending or forwarding node to retransmit a packet if necessary and enable implicit or/and explicit acknowledgment for multicast services. Simulations are performed in order to assess the performance of these schemes in terms of number of retransmissions, …
Multicast TV over WLAN in a University Campus Network
2009
One of the multimedia services offered by the campus network of the Polytechnic University of Valencia is TV over IP. This service works well in the devices connected directly to the wired network but we have detected some problems when the receivers access to the campus network through wireless IEEE 802.11, especially when devices roam across the Campus. In this paper we propose and evaluate a server-based solution to minimize the packet loss and reduce the lack of service when the mobile devices roam from an Access Point to another Access Point in the wireless network. This solution uses a location system to modify the behaviour of standard multicasting protocols in order to get a near-se…
UWSim-NET: An Open-Source Framework for Experimentation in Communications for Underwater Robotics
2019
The communication with the remotely operated vehicles (ROV) in underwater applications are usually based on umbilical cables. The increase in the number of ROVs in cooperative interventions motivates the interest in underwater wireless communications. They have a high impact in robotic applications because of their limited performance in underwater scenarios. In this work we present UWSim-NET, an extension of the simulator for underwater robotics UWSim, which is based on the Robot Operating System (ROS). UWSim-NET integrates a communications module based on Network Simulator 3 (NS3) that allows to model the physical and data link layers. Experiments demonstrating the capabilities of UWSim-N…
Moderate-to-Strong Turbulence Generation in a Laboratory Indoor Free Space Optics Link and Error Mitigation via RaptorQ Codes
2016
Free Space Optics (FSO) is rapidly gaining interest as a line-of sight communication technology that offers capabilities similar - in terms of bandwidth and transfer rates - to optical fibre, also possessing several advantages compared with traditional radio frequency links. However, FSO link quality can be strongly affected by unfavourable weather conditions and also by the phenomenon of optical turbulence, even in clear sky. In this work, we have implemented an indoor FSO link and generated moderate-to-strong turbulence conditions along the optical path by using heaters and a mechanical ventilation system. In this way, we have been able to investigate the effects of the generated turbulen…
Performance Analysis of Synchronous Duty-Cycled MAC Protocols
2015
In this letter, we propose an analytical model to evaluate the performance of the S-MAC protocol. The proposed model improves the accuracy of previous models in two aspects. First, it incorporates the dependence among the nodes within a cluster by defining a DTMC that models the number of active nodes, whereas the previous models considered that nodes were mutually independent. Second, it proposes new methods for calculating packet delay and energy consumption. The analytical model is validated through discrete-event based simulations. Numerical results demonstrate that the proposed analytical model and methods yield accurate results under realistic assumptions
An intrusion detection system for selective forwarding attack in IPv6-based mobile WSNs
2017
Selective forwarding attack is considered among the most dangerous attack in wireless sensor networks, particularly in mobile environment. The attackers compromise legitimate nodes and selectively drop some packets. In addition to that, the movement of some nodes increases link failures, collisions and packet loss. So, it will be more difficult to detect malicious nodes from legitimates ones. This paper focuses on detecting selective forwarding attackers in IPv6-based mobile wireless sensor networks when the standardized IPv6 Routing Protocol for Low Power and Lossy Networks (RPL) is used. Contrarily to previous works which propose solutions to detect selective forwarding attack in static w…
Performance of H.264 compressed video streams over 802.11b based MANETs
2004
We address the problem of video streams transmission in 802.11b based mobile ad-hoc networks (MANETs). Through the study of the delivery of a live encoded video stream, we expose the characteristics of different routing protocols and the infeasibility to provide QoS. The analysis shows the impact of a MANET on H.264 real-time video flows in terms of packet loss, end-to-end delay, jitter and distortion, and the behavior of H.264 error resilience tools in order to determine their effectiveness on such network scenarios. The results show that video traffic has demands that are hard to be met by a standard MANET, and that improvements are required in terms of routing protocols and QoS provision…