| 1. |
- Almers, Peter, et al.
(author)
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Exercises
- 2005
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In: Wireless Communications. - 9780470848883 - 047084888X - 0470848871 ; , s. 561-593
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Book chapter (other academic/artistic)
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| 2. |
- Florén, Britta, et al.
(author)
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Förstudie: Smart och klimatmedveten matbutik för morgondagens konsumenter och samhälle
- 2019
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Reports (other academic/artistic)abstract
- Vid sidan om transporter och bostäder så står maten för en av de stora klimatutmaningarna nu och framöver. Matens del av den totala konsumtionsdrivna klimatpåverkan i Sverige är idag cirka 25 %, ca 2 ton CO2-e per person och år. Genom att underlätta för konsumenter att välja mer klimatsmarta val vid livsmedelsinköp finns en möjlighet att minska klimatpåverkan från livsmedel. I ett nudgingförsök på mat.se sänkte medverkande kunder sin klimatpåverkan från livsmedel med 7 procent baserat på genomsnittliga kg CO2-e per order. Under motsvarande period minskade icke-deltagande konsumenter sitt klimatavtryck med 3 procent med samma beräkningsmetod. Förstudien har undersökt hur information om klimatpåverkan hos olika livsmedel tillsammans med tillgängliggörandet av klimatsmartare alternativ (nudging) kan förändra köpbeteendet hos konsumenten. Målet har varit att minska klimatpåverkan i staden. Förstudien har fokuserat på metoder och parametrar viktiga för att locka fler att medvetet eller omedvetet handla mer miljö-/klimat-smartare mat. Livskraftiga städer som uppmuntrar till hållbara livsstilar kräver innovativa lösningar som underlättar för konsumenten att välja rätt. Projektupplägget har bestått av en kartläggning av nuvarande situation, nudgingförsök samt projektworkshops. Kartläggningen genomfördes för att avgöra vilka produkter som är av specifikt intresse att tillgängliggöra klimatsmartare alternativ. RISE klimatdatabas för livsmedel har varit central i denna del för att identifiera vilka beslutsval som har kapacitet att ge en betydande klimatnytta. Nudgingförsöket har byggts upp i en två-stegs nudgingmodell där konsumenterna först har aktivt fått välja att medverka i projektet (steg 1). För de som väljer att förbinda sig till detta har klimatsmartare alternativ lyfts upp till det först visade alternativet vid vissa specifika sökord (steg 2). Projektdeltagare: - Mat.se, en innovativ aktör inom e-handel som vill utveckla lösningar för en minskad klimatpåverkan från livsmedelskonsumtion.- Göteborg Stad deltog som representant för medborgaren och staden, - Handelshögskolan (GU) med forskningsexpertis inom nudging. - RISE, experter inom livsmedels klimatpåverkan och beteendevetenskap.
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| 3. |
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| 4. |
- Florén, Fredrik
(author)
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Aspects on Interference and Diversity in Wireless Networks
- 2005
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Doctoral thesis (other academic/artistic)abstract
- This thesis deals with two topics in wireless communications: interference between frequency-hopping (FH) networks, and multiuser diversity. The work on FH treats a system where FH is used to provide simultaneous access to the channel for multiple uncoordinated wireless networks. This is achieved by performing frequency hops on a packet-by-packet basis, and letting the sequence of hopping frequencies be pseudo random. Furthermore, the networks in the considered system are allowed to use several packet types, which can be of different lengths. A throughput analysis of this system is performed, and this analysis is based mainly on two assumptions. Firstly, collisions, i.e., overlaps in time and frequency between packets, are assumed to always result in a total loss of the data in the colliding packets. Secondly, it is assumed that networks are asynchronous. Both exact and approximate expressions for the throughput are derived, and the dependence of the throughput on the number of networks and the available packet types is investigated for two existing wireless systems, namely Bluetooth and IEEE 802.11 FHSS. Furthermore, the accuracy of the collision assumption as a function of the distance between networks is determined for the Bluetooth system. The second topic of this thesis, multiuser diversity, is a scheme where a base station collects channel state information from a number of users and then transmits to the user with the instantaneously best channel. Although this scheme promises large gains, there are a number of practical aspects that reduce this gain. In this thesis two of these aspects are considered. Firstly, the impact of quantizing the feedback of the users' signal-to-noise ratio measurements is investigated for both variable- and constant-rate transmission. It is shown that even for a coarse quantization, the multiuser diversity gain is significant and good performance is achieved. Secondly, the impact of feedback delay is analyzed while also taking into account the additional diversity, referred to as link diversity, that Rake reception or transmit diversity (using space--time block codes) can provide. Expressions for the error rates and spectral efficiencies for uncoded constant- and variable-rate transmission are derived, and the dependence on the number of users, the feedback delay, and the link diversity order is investigated. These expressions also apply to Rake reception combined with transmit or receive antenna selection.
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| 5. |
- Florén, Fredrik, et al.
(author)
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Dependence of the mean SNR on the interaction between multiuser diversity, multipath diversity, and feedback delay
- 2005
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In: 2005 IEEE 61st Vehicular Technology Conference. VTC2005- Spring. - 0780388879 ; , s. 1898-1902
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Conference paper (peer-reviewed)abstract
- We examine wireless systems employing Rake receivers and fast scheduling over multiple users. The interactions between multipath diversity, multiuser diversity, and the feedback delay are investigated in terms of the mean signal-to-noise ratio (SNR). It is assumed that all users experience the same propagation characteristics, i.e., the same number of taps and power-delay profile (PDP). The results are exact as well as asymptotic (in the number of users) expressions that quantify this interaction. It is found that as the number of taps in the channel increases, the multiuser diversity gain decreases but better robustness against feedback delay is achieved. Furthermore, the asymptotic results derived show good agreement with the exact results for an exponential PDP, even for few users. Thus, we obtain expressions for the mean SNR that are compact and easy to evaluate
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| 6. |
- Florén, Fredrik, et al.
(author)
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The Effect of Feedback Quantization on the Throughput of a Multiuser Diversity Scheme
- 2003
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In: Conference Record / IEEE Global Telecommunications Conference. ; 1, s. 497-501
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Conference paper (peer-reviewed)abstract
- The impact of the quantization of SNR measurements on the throughput of a multiuser diversity scheme for constant-rate transmission is investigated under a block-Rayleigh fading assumption. In the downlink, each user measures its SNR, quantizes it, and feeds it back to the transmitter, which transmits a packet to the user with the highest quantized SNR. In the case of several users having the same quantized SNR, one of them is selected at random. It is concluded that using only a few quantization levels can yield a throughput that is only slightly less than the throughput obtained by using unquantized feedback.
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| 7. |
- Florén, Fredrik, et al.
(author)
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Throughput analysis of strongly interfering slow frequency-hopping wireless networks
- 2001
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In: Proc. IEEE Vehicular Technology Conference. - 0780367286 ; 1, s. 496-500
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Conference paper (peer-reviewed)abstract
- We derive an approximation for the throughput of strongly interfering frequency-hopping wireless networks, where packet collisions always result in lost data. A system is defined to consist of a certain number of radio networks, each with an arbitrary number of communicating units, coordinated to communicate without interference. Using the approximation, we estimate upper and lower bounds on system throughput, as well as the number of networks which gives maximum system throughput
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| 8. |
- Florén, Fredrik, et al.
(author)
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Throughput analysis of three multiuser diversity schemes
- 2003
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In: 57th IEEE Semiannual Vehicular Technology Conference. VTC 2003 (Cat. No.03CH37431). - 0780377575 ; , s. 2686-2690
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Conference paper (peer-reviewed)abstract
- The throughput of three slot allocation schemes for the downlink of a wireless TDMA system are investigated under the assumption of block-Rayleigh fading. The schemes use the instantaneous SNR at the users in order to take advantage of the independent fading of the channels. In the first scheme, which has been proposed earlier (R. Knopp et al., 1995), the base station transmits to the user that experiences the largest SNR in every slot. In the second scheme, which is a variant of an existing scheme (P. Viswanath et al., June 2002), the user with highest ratio between instantaneous SNR and mean SNR is transmitted to. Lastly, we propose a scheme that compares the SNR at a user to a threshold in order determine if transmission to that user shall occur. If the SNR is below the threshold, transmission to another user is attempted. The results indicate that considerable throughput gains can be achieved even with limited SNR feedback, although there exists a trade-off between throughput and delay
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| 9. |
- Florén, Fredrik, et al.
(author)
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Throughput of strongly interfering slow frequency-hopping networks
- 2004
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In: IEEE Transactions on Communications. - 0090-6778. ; 52:7, s. 1152-1159
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Journal article (peer-reviewed)abstract
- With the increasing, use of short-range wireless devices for high-data-rate communication in the shared frequency bands, the level of interference can be expected to increase. The ability to,estimate, the performance degradation of these devices due to increasing interference is, therefore, important. In this paper, the throughput of devices that perform frequency hops after each transmitted packet in order to achieve diversity is investigated. The system model allows for an analysis of systems where packets of variable durations are used, and the throughput derivation is based on the assumption that collisions result in a total loss of the data in the colliding packets. The resulting expression for the throughput is given as a function of the number of frequency channels used for frequency hopping, the number of interfering networks, the durations of the packet types available, and the probability of networks selecting a certain packet type for transmission. An approximation of the exact expression for the throughput is also derived, and the results are applied to an example system consisting of Bluetooth piconets.
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| 10. |
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