Search results for "Link level"

showing 6 items of 6 documents

Performance comparison of HARQ and ARQ mechanisms in IEEE 802.16 networks

2008

The IEEE 802.16 technology defines several link level mechanisms to retransmit erroneous data. In this paper we compare the performance of the ARQ and HARQ mechanisms in the IEEE 802.16 networks. Our simulations results show that in general HARQ provides a better performance. However, ARQ can compete successfully with it due to a smaller signaling overhead. Furthermore, since ARQ does not require a dedicated uplink signaling channel for the acknowledgments messages, it results in better resources utilization in the uplink direction.

IEEE 802Computer sciencebusiness.industryComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKSHybrid automatic repeat requestData_CODINGANDINFORMATIONTHEORYSelective Repeat ARQPerformance comparisonTelecommunications linkOverhead (computing)Link levelbusinessCommunication channelComputer networkProceedings of the 11th international symposium on Modeling, analysis and simulation of wireless and mobile systems
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Link Adaptation Thresholds for the IEEE 802.16 Base Station

2008

The IEEE 802.16 technology defines a number of modulation and coding schemes that the base station can use to achieve the best tradeoff between the spectrum efficiency and the resulting application level throughput. However, the 802.16 specification does not define any particular link level adaptation algorithm, neither does it specify the SNR thresholds to switch between modulation and coding schemes. In this paper we consider a link adaptation model and conduct a number of simulation runs to find transition thresholds for ARQ and HARQ retransmission mechanisms. All the simulations are done with the 802.16 extension for the NS-2 simulator.

IEEE 802Computer sciencebusiness.industryRetransmissionComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKSReal-time computingHybrid automatic repeat requestLink adaptationData_CODINGANDINFORMATIONTHEORYSpectral efficiencyBase stationLink levelbusinessComputer networkCoding (social sciences)Proceedings of the 3rd International Conference on Performance Evaluation Methodologies and Tools
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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 spreading factor interferenceSettore ING-INF/03 - TelecomunicazioniNetwork packetComputer sciencebusiness.industry010401 analytical chemistryinterference020206 networking & telecommunications02 engineering and technologyLoRa01 natural sciences0104 chemical sciencesComputer Science ApplicationsPacket lossModulationModeling and Simulation0202 electrical engineering electronic engineering information engineeringChirpspreading factorLink levelImperfectElectrical and Electronic EngineeringbusinessComputer networkIEEE Communications Letters
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Performance of LoRa technology: link-level and cell-level performance

2020

Abstract LoRa is a chirp spread spectrum technology that is becoming very popular for low-power wide-area networks, with high-density devices. In this chapter, we study the capacity of LoRa in rejecting different interfering signals. First, we analyze LoRa modulation numerically demonstrating that channel captures appear easily and that collisions between packets modulated with different spreading factors (SFs) are not uncommon. We validate such findings in experiments based on commercial devices and software-defined radios. Second, we model the network capacity obtainable in a typical LoRa cell: we show that high SFs can be seriously influenced by inter-SF collisions and that fading has a …

Settore ING-INF/03 - Telecomunicazionibusiness.industryComputer scienceNetwork packetLoRa IoTspreading factorinterferencecapacityperformanceChirp spread spectrumCellular levelModulationDefault gatewayLink levelFadingbusinessCommunication channelComputer network
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An explanation for unexpected 802.11 outdoor link-level measurement results

2008

This paper provides experimental evidence that "weird'/poor outdoor link-level performance measurements may be caused by driver/card-specific antenna diversity algorithms unexpectedly supported/activated at the WLAN transmitter side. We focus our analysis on the Atheros/MADWiFi card/driver case, and we observe that the transmit antenna diversity mechanisms remain by default enabled when the available antennas are not homogeneous in terms of gain or, even worse, when only a single antenna is connected. This may cause considerable performance impairments (large frame loss ratio), in conditions frequently encountered in outdoor link deployments. The negative impact of transmit antenna diversit…

Transmission (telecommunications)business.industryComputer scienceSettore ING-INF/03 - TelecomunicazioniFrame (networking)TransmitterLink levelBroadcastingAntenna (radio)UnicastTelecommunicationsbusinessAntenna diversity
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WINSE: WiMAX NS-2 extension

2009

IEEE 802.16 standard defines the wireless broadband technology called WiMAX. When compared to other wireless technologies, it introduces many interesting advantages at PHY, MAC, and QoS layers. Heavy simulations are needed to study IEEE 802.16 performance and propose further enhancements to this standard. Link level simulations are not always sufficient, while system level simulators are not always accurate to capture MAC and transport protocol details. We implemented a 802.16 extension for the NS-2 network simulator. It includes upper PHY modeling, almost all the features of the 802.16 MAC layer, as well as the QoS framework. This article describes the implemented features, simulation meth…

Wireless broadbandIEEE 802.11w-2009Computer sciencebusiness.industryInter-Access Point ProtocolQuality of serviceComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKSLink levelIEEE 802.1XNetwork allocation vectorbusinessWiMAXComputer networkProceedings of the Second International ICST Conference on Simulation Tools and Techniques
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