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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.
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.
Increasing the VoIP Capacity through MAP Overhead Reduction in the IEEE 802.16 OFDMa Systems
2010
One of the main issues with supporting VoIP service over 802.16 networks is the signalling overhead caused by the downlink MAP messages due to frequent transmissions and small packets. To decrease the MAP overhead, the 802.16 standard proposes some mechanisms, such as the compressed MAP and sub-MAPs. In this paper, we show by means of extensive dynamic simulations that sub-MAPs can reduce dramatically the signalling overhead associated with VoIP traffic and significantly improve overall VoIP capacity. At the same time, since sub-MAPs are more sensitive to packet drops, they tend to increase the number of HARQ retransmissions in downlink and transmission delays in the uplink direction.
Analysis of the Non-Transparent In-Band Relays in the IEEE 802.16 Multi-Hop System
2010
This paper presents extensive dynamic simulations of the non-transparent in-band relays working in the distributed scheduling mode. The simulation results show that in-band relays can improve noticeably the spectral efficiency without acquiring an additional radio spectrum. Also, packet transmission delays become smaller. An important outcome of the dynamic simulations is that it is very crucial to choose a correct relay zone size where the base station and relay nodes exchange data. Otherwise, throughput fairness of the whole system declines. It indicates an importance of the relay zone size adjustment algorithm that the base station must run.
ARQ parameters for VoIP in IEEE 802.16 networks
2009
IEEE 802.16 standard defines two data retransmission mechanisms. HARQ provides fast retransmissions in cost of slightly increased overhead. On the contrary, ARQ has less overhead in cost of bit longer delays. It is therefore often used with BE connections. In addition to delay tolerant applications, BE can also be used for real-time services. Therefore, in this paper we analyze the ARQ mechanism and provide guidelines on how to set the ARQ parameters to achieve a good balance between the VoIP delay and packet loss.
Impact of portable device restrictions on IEEE 802.16 performance
2008
IEEE 802.16 is a good alternative for fast wireless connection in the next generation portable information devices (PID). However it was not originally designed for portable devices, but mobility was added later to the specification. This means that the lack of resources on portable devices might have a significant impact on which IEEE 802.16 features should be chosen and how they should be used. Proper usage of ARQ can increase the IEEE 802.16 performance but it can also require much resources from PIDs. In this paper we focus on how ARQ features are affected by limited resources on PID and how much the limitations affect on the performance.
Lessons from the 2018-2019 European droughts : a collective need for unifying drought risk management
2022
Funding Information: This open-access publication was funded by the University of Freiburg. Funding Information: Financial support. The project is supported by the Wassernetzwerk Baden-Württemberg (Water Research Network of the State Baden-Württemberg), which is funded by the Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg (Ministry of Science, Research and the Arts of the State Baden-Württemberg) (grant no. AZ. 7532.21/2.1.6) and Maa-ja vesitekniikan tuki ry foundation. Doris E. Wendt acknowledges her support as part of the NERC-funded Groundwater Drought Initiative (NE/R004994/1). Lucy J. Barker was supported by the Natural Environment Research Council (NE/R016429/1) a…
Associations between parental rules, style of communication and children's screen time
2015
Background Research suggests an inverse association between parental rules and screen time in pre-adolescents, and that parents’ style of communication with their children is related to the children’s time spent watching TV. The aims of this study were to examine associations of parental rules and parental style of communication with children’s screen time and perceived excessive screen time in five European countries. Methods UP4FUN was a multi-centre, cluster randomised controlled trial with pre- and post-test measurements in each of five countries; Belgium, Germany, Greece, Hungary and Norway. Questionnaires were completed by the children at school and the parent questionnaire was brough…
SICUREZZA E TOLLERABILITA' DEL TRATTAMENTO LOCALE CON ILOPROST IN PAZIENTI AFFETTI DA MALATTIA DI LA PEYRONIE. STUDIO PILOTA DI FASE 1 E PROPOSTA DI …
2010
Purpose. Intralesional therapy is a less invasive method for the treatment of Peyronie's disease. The objective of this study was to evaluate safety and tolerability of intralesional injections of Iloprost (I2 Prostacyclin analogue) for its property to suppress in fibroblasts CTFG (Connective tissue growth factor) production, which acts in concert with TGF-ß to stimulate the fibrotic process.?Methods. Nineteen patients with Peyronie's disease were preliminarily evaluated by considering the degree of penile curvature, plaque size and local and systemic symptoms. Each patient then received weekly intralesional injections of 200ng of Iloprost in 1 ml of normal saline for 4-5 weeks. If tolerate…
The reason for a project that was never performed: Alvar Aalto and the residential complex in Pavia (1966-68)
2015
This paper aims to analyze the characteristics of the project for the residential complex "Patrizia" in Pavia by Alvar Aalto (1966-1968). Although not realized, for political and economic reasons, the project offers an interesting example of urban planning in an “organic key”. In particular, this paper aims to contextualize the project of Aalto in the broader context of the residential building in Italy after World War II, when the problems of reconstruction and "home" are the heart of the debate on architecture. The project, in fact, takes place in the years immediately following the experiments of the social housing plan INA CASA (1949-63), which - with differences in design and architect…