| 1. |
- Voicu, Andra M., et al.
(författare)
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Modelling Large-Scale CSMA Wireless Networks
- 2021
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Ingår i: 2021 IEEE Wireless Communications and Networking Conference (WCNC). - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- Increasingly more wireless devices adopt CSMA at the MAC layer, primarily due to the ubiquitous utilization of Wi-Fi, but also due to the development of new standards that implement CSMA variants, like LAA-LTE. It is thus critical to use reliable modelling tools that accurately evaluate the performance of large-scale CSMA deployments, as expected in practice. This paper compares the accuracy and computational efficiency of stochastic geometry modelling (SGM) and our proposed hybrid model, for estimating the MAC-layer throughput and signal-to-interference-and-noise ratio (SINR) of large-scale CSMA wireless deployments. Using ns-3 simulations as the baseline reference, we show that our hybrid model is significantly more accurate and at least one order of magnitude faster to compute than SGM. SGM underestimates the SINR, yet as it neglects the sensing overhead, it usually overestimates the MAC-layer throughput substantially. We thus argue that our hybrid model is preferable to SGM for modelling large-scale CSMA deployments.
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| 2. |
- Voicu, Andra M., et al.
(författare)
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Risk-Informed Interference Assessment for Shared Spectrum Bands : A Wi-Fi/LTE Coexistence Case Study
- 2017
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Ingår i: IEEE Transactions on Cognitive Communications and Networking. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2332-7731. ; 3:3, s. 505-519
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Tidskriftsartikel (refereegranskat)abstract
- Interference evaluation is crucial when deciding whether and how wireless technologies should operate. In this paper, we demonstrate the benefit of risk-informed interference assessment to aid spectrum regulators in making decisions, and to readily convey engineering insight. We apply, for the first time, risk assessment to an open question of inter-technology spectrum sharing, i.e., a Wi-Fi/LTE coexistence study in the unlicensed band, and we demonstrate that this method comprehensively quantifies the interference impact. We perform simulations with our newly publicly available tool and we consider throughput degradation and fairness as example metrics to assess the risk for different network densities, numbers of channels, and deployments. The risk assessment study shows that no regulatory intervention is needed to ensure harmonious technical Wi-Fi/LTE coexistence: for the typically large number of channels available in the 5 GHz band, the risk for Wi-Fi from LTE is negligible. As an engineering insight, Wi-Fi coexists better with itself in dense deployments, but better with LTE in sparse deployments. Also, both main LTE-in-unlicensed variants coexist well with Wi-Fi in general. For LTE intra-technology inter-operator coexistence, both variants typically coexist well in the 5 GHz band, but for dense deployments, implementing listen-before-talk causes less interference.
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| 3. |
- Voicu, Andra M., et al.
(författare)
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Survey of Spectrum Sharing for Inter-Technology Coexistence
- 2019
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Ingår i: IEEE Communications Surveys and Tutorials. - : Institute of Electrical and Electronics Engineers (IEEE). - 1553-877X. ; 21:2, s. 1112-1144
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Tidskriftsartikel (refereegranskat)abstract
- Increasing capacity demands in emerging wireless technologies are expected to be met by network densification and spectrum bands open to multiple technologies. These will, in turn, increase the level of interference and also result in more complex inter-technology interactions, which will need to be managed through spectrum sharing mechanisms. Consequently, novel spectrum sharing mechanisms should be designed to allow spectrum access for multiple technologies, while efficiently utilizing the spectrum resources overall. Importantly, it is not trivial to design such efficient mechanisms, not only due to technical aspects, but also due to regulatory and business model constraints. In this survey we address spectrum sharing mechanisms for wireless inter-technology coexistence by means of a technology circle that incorporates in a unified, system-level view the technical and nontechnical aspects. We thus systematically explore the spectrum sharing design space consisting of parameters at different layers. Using this framework, we present a literature review on inter-technology coexistence with a focus on wireless technologies with equal spectrum access rights, i.e., (i) primary/primary, (ii) secondary/secondary, and (iii) technologies operating in a spectrum commons. Moreover, we reflect on our literature review to identify possible spectrum sharing design solutions and performance evaluation approaches useful for future coexistence cases. Finally, we discuss spectrum sharing design challenges and suggest future research directions.
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| 4. |
- Voicu, Andra M., et al.
(författare)
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The Importance of Adjacent Channel Interference : Experimental Validation of ns-3 for Dense Wi-Fi Networks
- 2017
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Ingår i: Proceedings Of The 20th ACM International Conference On Modelling, Analysis and Simulation of Wireless And Mobile Systems (MSWIM'17). - New York, NY, USA : Association for Computing Machinery (ACM). - 9781450351645 ; , s. 43-52
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Konferensbidrag (refereegranskat)abstract
- In its evolution to provide ever higher data rates, the Wi-Fi standard has incorporated sophisticated PHY-layer techniques, which has in turn increased the complexity of network-wide interference relationships. Proper modelling of the resulting inter-device interactions is crucial for accurately estimating Wi-Fi network performance, especially in the contemporary context of traffic and network densification. Event-driven simulators like the open-source ns-3 are in principle able to capture these interactions, however it is imperative to validate, against experimental results, whether their underlying models reflect the network behaviour in practice. In this paper we first perform experiments in a large-scale indoor testbed to validate the IEEE 802.11ac Wi-Fi model in ns-3, for various channel width and allocation configurations. Our results show that ns-3 captures Wi-Fi co-channel interactions with reasonable precision, but fails to model adjacent channel interference (ACI), which our experiments show to be critical in dense networks. We therefore propose and implement an ACI model in ns-3. Importantly, our model successfully captures the qualitative behaviour of the CSMA/CA mechanism when transmissions on adjacent channels occur. Further, our ACI implementation significantly improves the accuracy of both the network and per-device throughput estimates for the considered dense IEEE 802.11ac network compared to the basic ns-3 Wi-Fi model without ACI. For example, without ACI modelling, ns-3 overestimates the aggregate network throughput by up to 230%, whereas with our ACI implementation the aggregate throughput estimate is no more than 65% higher than the experimental results.
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| 5. |
- Voicu, Andra M., et al.
(författare)
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Wi-Fi Evolution for Future Dense Networks : Does Sensing Threshold Adaptation Help?
- 2018
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Ingår i: 2018 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC). - : IEEE. - 9781538617342
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Konferensbidrag (refereegranskat)abstract
- Emerging Wi-Fi technologies are expected to cope with large amounts of traffic in dense networks. Consequently, proposals for the future IEEE 802.11ax Wi-Fi amendment include sensing threshold and transmit power adaptation, in order to improve spatial reuse. However, it is not yet understood to which extent such adaptive approaches - and which variant - would achieve a better balance between spatial reuse and the level of interference, in order to improve the network performance. Moreover, it is not clear how legacy Wi-Fi devices would be affected by new-generation Wi-Fi implementing these adaptive design parameters. In this paper we present a thorough comparative study in ns-3 for four major proposed adaptation algorithms and we compare their performance against legacy non-adaptive Wi-Fi. Additionally, we consider mixed populations where both legacy non-adaptive and new-generation adaptive populations coexist. We assume a dense indoor residential deployment and different numbers of available channels in the 5 Wiz band, relevant for future IEEE 802.11ax. Our results show that for the dense scenarios considered, the algorithms do not significantly improve the overall network performance compared to the legacy baseline, as they increase the throughput of some nodes, while decreasing the throughput of others. For mixed populations in dense deployments, adaptation algorithms that improve the performance of new-generation nodes degrade the performance of legacy nodes and vice versa. This suggests that to support Wi-Fi evolution for dense deployments and consistently increase the throughput throughout the network, more sophisticated algorithms are needed, e.g. considering combinations of input parameters in current variants.
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