| 51. |
- Alfredsson, Stefan, 1976-, et al.
(författare)
-
Transport Protocol Performance over 4G Links: Emulation Methodology and Results
- 2006
-
Ingår i: Proceedings of the International Symposium on Wireless Communication Systems (ISWCS). - : IEEE Computer Society. - 9781424403981 ; , s. 327-332
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a wireless link and network emulator for the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at the physical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the physical/link layer in such a downlink. The paper introduces the Wireless IP system, describes the emulator design and implementation, and presents experimental results with TCP in combination with various physical/link layer parameters. The impact of link layer ARQ persistency, adaptive modulation, prediction errors and simple scheduling are all considered.
|
|
| 52. |
- Algervik, Robert, 1981-
(författare)
-
Embedding Theorems for Mixed Norm Spaces and Applications
- 2008
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is devoted to the study of mixed norm spaces that arise in connection with embeddings of Sobolev and Besov type spaces. The work in this direction originates in a paper due to Gagliardo (1958), and was continued by Fournier (1988) and by Kolyada (2005). We consider fully anisotropic mixed norm spaces. Our main theorem states an embedding of these spaces into Lorentz spaces. Applying this result, we obtain sharp embedding theorems for anisotropic fractional Sobolev spaces and anisotropic Sobolev-Besov spaces. The methods used are based on non-increasing rearrangements and on estimates of sections of functions and sections of sets. We also study limiting relations between embeddings of spaces of different type. More exactly, mixed norm estimates enable us to get embedding constants with sharp asymptotic behaviour. This gives an extension of the results obtained for isotropic Besov spaces $B_p^\alpha$ by Bourgain, Brezis, and Mironescu, and for Besov spaces $B^{\alpha_1,\dots,\alpha_n}_p$ by Kolyada. We study also some basic properties (in particular the approximation properties) of special weak type spaces that play an important role in the construction of mixed norm spaces and in the description of Sobolev type embeddings.
|
|
| 53. |
- Ali Yahiya, Tara, et al.
(författare)
-
Seamless Interworking of WLAN and WMAN Wireless Networks
- 2006
-
Konferensbidrag (refereegranskat)abstract
- Future network environments will be heterogeneous and mobile terminals will have the opportunity to dynamically select among many different access technologies. Therefore, it is important to provide service continuity in case of vertical handovers when terminals change the access technology. Two important wireless access technologies are WLAN (Wireless Local Access Networks) and WMAN (Wireless Metropolitan Access Networks) networks. In this paper, we address several challenges related to a seamless integration of those technologies. We highlight important aspects for designing a WLAN/WMAN interworking architecture and we address important Quality of Service (QoS) issues for such interworked systems like degree of QoS support provided by the technologies, QoS mapping and signalling for vertical handover. By formulating several interworking scenarios, where WLAN users with ongoing voice, video and data sessions hand over to WMAN, we study QoS and performance issues and analyse feasibility of seamless session continuity through simulations
|
|
| 54. |
- All, Rainar, et al.
(författare)
-
Olyckor, riskanalyser och säkerhetsarbete : Några olika perspektiv inom Räddningsverket
- 2006
-
Annan publikation (populärvet., debatt m.m.)abstract
- SammanfattningSyftet med denna kartläggning har varit att ge en nulägesbild över hur riskanalyser, riskbedömningar och riskvärderingar sker i Räddningsverkets arbete med skydd mot olyckor. Ett syfte har också varit att beskriva de olika strategier för säkerhetsarbete som tillämpas i myndigheten.Kartläggningen har utförts genom gruppintervjuer under perioden oktober 2004 mars 2005 och har följts upp med hjälp av två seminarier i november 2005. Analysgruppen har bestått av medarbetare vid Räddningsverkets sekretariat för forskning och analys.Resultaten visar bland annat att:- verkets arbete utgår från en kompott av olyckor, skador och händelser, var och en med sin egen logik baserad på tradition, lagstiftning och politisk inriktning- arbetet bedrivs utifrån en mångfald av strategier som i många fall inte är produkten av genomtänkta analyser och medvetna val- verkets olika roller behöver närmare analyseras och kopplas till tydligarestrategier och metoder för arbetet med skydd mot olyckor- säkerhetsarbete och riskhantering är inte synonyma begrepp i myndigheten- det saknas myndighetsgemensamma begreppsdefinitioner inom det kartlagdaområdet- det råder en brist i myndigheten på djupare diskussioner och reflektioner kring värdegrunder och principer för riskvärdering.Rapporten behandlar många olika frågor som på olika sätt är relevanta för Räddningsverkets arbete på kort och lång sikt. I rapporten ges ett tiotal förslag till fortsatt arbete. Några förslag är att:- utarbeta en begreppspolicy för myndigheten- utarbeta information till privatpersoner som lagenliga skyldigheter inom det olycksförebyggande området- satsa på kompetensutveckling internt- starta ett utvecklingsarbete inom riskvärdering- utveckla analysförmåga för framtidens olycksrisk- starta en idéverkstad för framtida säkerhetsarbeteKartläggningen ska ligga till grund för fortsatt utvecklingsarbete inom Räddningsverket. Delar av materialet kan också komma att utgöra underlag förutveckling av läromedel för verkets utbildningsverksamhet. Rapporten utgör också en möjlig källa för fortsatt forskning och analys inom området
|
|
| 55. |
- Allman, Mark, et al.
(författare)
-
Early Retransmit for TCP and SCTP
- 2008
-
Annan publikation (populärvet., debatt m.m.)abstract
- This document proposes a new mechanism for TCP and SCTP that can be used to recover lost segments when a connection's congestion window is small. The "Early Retransmit" mechanism allows the transport to reduce, in certain special circumstances, the number of duplicate acknowledgments required to trigger a fast retransmission. This allows the transport to use fast retransmit to recover packet losses that would otherwise require a lengthy retransmission timeout.
|
|
| 56. |
|
|
| 57. |
|
|
| 58. |
- Alm, Maria
(författare)
-
Teaching materials and students with mental retardation
- 2008
-
Konferensbidrag (populärvet., debatt m.m.)abstract
- Teaching materials and students with mental retardationFrom a socio-cultural perspective, teaching materials can be regarded as mediating tools for transferring culturally based knowledge, norms, values and traditions. While literature on teaching materials in general is substantial, few investigations have been conducted on teaching materials for students with mental retardation. In this paper I will present parts of an ongoing project in which this issue is focused. The study includes about twenty students in two training school classes and one class for students with mild mental retardation, covering the grades 7 10 in the compulsory school.Teaching materials in this study are defined as cultural tools used in education and serving a pedagogical function in programs for students with mental retardation (särskolan). My preliminary findings indicate predominance for everyday skills in teaching material activities. Reading or mathematical development in teaching material activities are of low priority. The activities often imply dilemmas the teacher have to master.
|
|
| 59. |
- Almang, Jan
(författare)
-
Affordances and the Nature of Perceptual Content
- 2008
-
Ingår i: International journal of philosophical studies (Print). - : Routledge. - 0967-2559 .- 1466-4542. ; 16:2, s. 161-177
-
Tidskriftsartikel (refereegranskat)abstract
- According to John McDowell, representational perceptual content is conceptual through and through. This paper criticizes this view by claiming that there is a certain kind of representational and non-conceptual perceptual content that is sensitive to bodily skills. After a brief introduction to McDowell's position, Merleau-Ponty's notion of body schema and Gibson's notion of affordance are presented. It is argued that affordances are constitutive of representational perceptual content, and that at least some affordances, the so-called 'conditional affordances', are essentially related to the body schema. This means that the perceptual content depends upon the nature of the body schema. Since the body schema does not pertain to the domain that our conceptual faculties operate upon, it is argued that this kind of perceptual content cannot be conceptual. At least some of that content is representational, yet it cannot feature as non-demonstrative conceptual content. It is argued that if it features as demonstrative conceptual content, it has to be captured by private concepts. Since McDowell's theory does not allow for the existence of a private language, it is concluded that at least some representational perceptual content is non-conceptual.
|
|
| 60. |
|
|
