| 11. |
- Berggren, Fredrik, et al.
(författare)
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Dynamic Spectrum Access, Phase 1 Scenarios and research challenges
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The currently used mechanisms for spectrum management are a contributing factor to the long lead times from innovation to market in wireless technologies andsystems. This has in turn been a major contributing factor to the dominance of the large telecom companies in the European and World markets, whereas very few innovative enterprises have exhibited consistent growth, although the technicalcompetence in Sweden is very high in this area. Alternative spectrum management regimes, such as the introduction of "unlicensed bands" have proven very effective in lowering entry thresholds for smaller companies (e.g the WLAN business). In addition, experts claim that the spectrum requirements for communication purposes will increase by as much as 200-300 % up to 2010. At the same time the actual usage of the electromagnetic spectrum is very inefficient.The project aims at studying new more, flexible, spectrum allocation regimeswhich, in combination with new technologies, such as multi-radio access, novelbroadband access techniques, software defined radio and spatial techniques (e.g.smart antennas, multi-hop schemes) have the potential of lowering the entry thresholds for new actors and provide radical improvement to the efficiency ofspectrum usage. Further the aim is to investigate the economic and regulatory consequences of such Dynamic Spectrum Access technologies and managementregimes. The results will provide input to future policies in spectrum management. The project has been divided into a first, pre-study phase and a second, research phase. The first phase was launched in Dec of 2004 and the second phase is planned to start in Jan 2005. The first phase of the project, reported here, has the aim toprovide a qualitative assessment of the potential benefits of dynamic spectrum access regimes. The analysis in the report and other studies in the area, indeed indicate there is a potential to both lower the entry thresholds for new actors as well as provide radical improvement to the efficiency of spectrum usage. The area isdefinitely of significant issues and the project should be continued studying the DSA concepts in more detail.Further, using a systematic procedure, a number of critical areas and bottleneck problems were identified. Our conclusion is that more research is needed in theseareas to achieve the above mentioned benefits. As `side effect' in this procedure, a number of novel and interesting spectrum management concepts were derived, e.g.the `real-time spectrum trading' and `use rights' concepts. Out of this gross list ofinterest problems, a number of highly important problems were selected, matching the competence of the project team. These problems are proposed to be the focus ofthe next phase in the project.Finally, the report provides an overview of the most important ongoing research and policy-making activities in the DSA-area.
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| 12. |
- Berggren, Fredrik, et al.
(författare)
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Energy-Effcient Control of Rate and Power in DS-CDMA Systems
- 2004
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Ingår i: IEEE Transactions on Wireless Communications. - : IEEE. - 1536-1276 .- 1558-2248. ; 3:3, s. 725-733
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Tidskriftsartikel (refereegranskat)abstract
- The quality of service in DS-CDMA can be controlled by a suitable selection of processing gain and transmission powers. In this paper, distributed control of rate and power for best effort data services is considered. In particular, we elaborate on the problem of how to control the transmission rates for maximizing system throughput while simultaneously minimizing the transmission powers. We assume a practical scenario, where every user has a finite set of discrete transmission rates and propose a simple heuristic rate allocation scheme, greedy rate packing (GRP), applicable in both upand downlink. The scheme can be interpreted as a practical form of water-filling, in the sense that high transmission rates are allocated to users having high link gains and low interference. We show that under certain conditions, GRP will give maximum throughput and that it can be extended to guarantee a minimum data rate while maximizing network excess capacity. We suggest and analyze a distributed power control control algorithm to control the intercell interference when GRP is applied to a multicellular system. Numerical results show that the proposed transmission scheme can significantly decrease the power levels while maintaining high throughput.
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| 13. |
- Berggren, Fredrik, et al.
(författare)
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Energy-Efficient Downlink Power Control and Scheduling for CDMA Non-Real Time Data
- 2000
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Konferensbidrag (refereegranskat)abstract
- The performance of CDMA systems highly depends on the success in managing interference arising from both intercell and intra-cell transmissions. Interference management in terms of power control has been widely studied. In this paper we consider non-real time data services, where in addition to power control, there is the possibility of scheduling intra-cell transmissions. One such schedule is to use time division so that users transmit in a one-by-one fashion within each cell. We com- bine this form of scheduling with a suggested distributed power control algorithm for the inter-cell interference management. We show that the algorithm converges to a power allocation that supports the non-real time data users with the minimum power while meeting requirements on average data rate.
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| 14. |
- Huang, L., et al.
(författare)
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ECDR2 : Error Corrector and Detector Relocation Router for Network-on-Chip
- 2020
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Ingår i: IEEE Transactions on Computers. - : IEEE Computer Society. - 0018-9340 .- 1557-9956.
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Tidskriftsartikel (refereegranskat)abstract
- Network-on-chip (NoC) is commonly used in modern many core systems due to its high bandwidth and flexibility. As the manufacturing process keeps scaling, the reliability challenge of NoCs becomes more significant. Error correction code (ECC) is wildly adopted in error correction NoCs to improve the data correctness. At the same time, extra stages are introduced in the router pipeline to embed the error correction capability. As a result, traditional error correction routers suffer from high network latency. Our research was motivated by this limitation and removes the extra pipeline stages introduced for error correction. In this brief, we propose an error correction router, called error corrector and detector relocation router (ECDR2), that achieves both low latency and high error correction capability. The ECDR2 architecture optimizes the pipeline flow of the router, and further improves the network latency. Experimental results show that, compared with the baseline design, ECDR^2 achieves 22.6% and 39.4% less average latency under uniform traffic pattern and Dedup benchmark, respectively in a 8×8 mesh NoC. The circuit area of ECR is also 7.9% less than that of the baseline design under 45nm technology
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| 15. |
- Kormi-Nouri, Reza, 1954-, et al.
(författare)
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The effect of bilingualism on letter and category fluency tasks in primary school children : advantage or disadvantage?
- 2012
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Ingår i: Bilingualism. - : Cambridge University Press. - 1366-7289 .- 1469-1841. ; 15:2, s. 351-364
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the current study was to examine the effects of bilingualism on letter and category fluency tasks. Participants were 1,600 monolingual and bilingual children from three cities in Iran: Tehran (Persian monolinguals), Tabriz (Turkish–Persian bilinguals), and Sanandaj (Kurdish–Persian bilinguals). We separately presented nine Persian letters and thirty-one categories to the participants, and asked them to generate as many words as possible using each of these initial letters and categories within a maximum of three minutes. Bilingual children generated more words than monolingual children in the letter fluency task; this effect was more pronounced in Grade 1 and for Turkish–Persian bilinguals. However, Persian monolinguals generated significantly more words than both bilingual groups in the category fluency task. Thus, bilingualism can be of both advantage and disadvantage, and produce a dissociative effect. We discuss the results on the basis of the specific nature and different cognitive demands of letter and category fluency tasks. We suggest that the degree of language proficiency of bilinguals should be considered as an important variable in future research on bilingualism.
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| 16. |
- Kormi-Nouri, Reza, 1954-, et al.
(författare)
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The effect of childhood bilingualism on episodic and semantic memory tasks
- 2008
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Ingår i: Scandinavian Journal of Psychology. - : Wiley. - 0036-5564 .- 1467-9450. ; 49:2, s. 93-109
-
Tidskriftsartikel (refereegranskat)abstract
- Kormi-Nouri, Moniri and Nilsson (2003) demonstrated that Swedish-Persian bilingual children recalled at a higher level than Swedish monolingual children, when they were tested using Swedish materials. The present study was designed to examine the bilingual advantage of children who use different languages in their everyday life but have the same cultural background and live in their communities in the same way as monolingual children. In four experiments, 488 monolingual and bilingual children were compared with regard to episodic and semantic memory tasks. In experiments 1 and 2 there were 144 boys and 144 girls in three school groups (aged 9-10 years, 13-14 years and 16-17 years) and in three language groups (Persian monolingual, Turkish-Persian bilingual, and Kurdish-Persian bilingual). In experiments 3 and 4, there were 200 male students in two school groups (aged 9-10 years and 16-17 years) and in two language groups (Persian monolingual and Turkish-Persian bilingual). In the episodic memory task, children learned sentences (experiments 1-3) and words (Experiment 4). Letter and category fluency tests were used as measures of semantic memory. To change cognitive demands in memory tasks, in Experiment 1, the integration of nouns and verbs within sentences was manipulated by the level of association between verb and noun in each sentence. At retrieval, a recognition test was used. In experiments 2 and 3, the organization between sentences was manipulated at encoding in Experiment 2 and at both encoding and retrieval in Experiment 3 through the use of categories among the objects. At retrieval, free recall or cued recall tests were employed. In Experiment 4, the bilingual children were tested with regard to both their first and their second language. In all four experiments, a positive effect of bilingualism was found on episodic and semantic memory tasks; the effect was more pronounced for older than younger children. The bilingual advantage was not affected by changing cognitive demands or by using first/second language in memory tasks. The present findings support the cross-language interactivity hypothesis of bilingual advantage.
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| 17. |
- Kurti, Erdelina, et al.
(författare)
-
Using Systems Thinking to Illustrate Digital Business Model Innovation
- 2021
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Ingår i: Systems. - : MDPI. - 2079-8954. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- Digital business model innovation is discussed by bringing together systemic innovation and digital innovation. Applying the Rich Picture technique, the complexity transpiring in the digital innovation of the business models is illustrated. Further, a real world example is presented and discussed in relation to systemic innovation and digital innovation. This study further contributes by shedding light on the added complexity brought by digital innovation but also the need for a combined and mixed systems thinking approach.
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| 18. |
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| 19. |
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| 20. |
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