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Sökning: LAR1:miun > Kungliga Tekniska Högskolan > (1995-1999)

  • Resultat 1-10 av 19
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  • Berg, Miguel (författare)
  • Concept for hybrid random/dynamic radio resource management
  • 1998
  • Ingår i: Proceedings of the 1998 9th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC '98. Part 3; Boston, MA, USA; 8 Sept. - 11 Sept. 1998. Vol. 1. - New York : IEEE. ; , s. 424-428, s. 424-428
  • Konferensbidrag (refereegranskat)abstract
    • Third generation mobile communication systems will allow many different services with varying demands on data rate and delay. For those systems, the fixed radio resource management (RRM) techniques used in today's low rate systems will not be appropriate to ensure efficient utilization of the radio spectrum. Dynamic RRM is necessary in order to cope with the large variations in data rate. We study the bunch concept which is a hybrid between random and dynamic RRM. Within a small synchronized cluster (bunch) we use dynamic radio resource allocation combined with SIR-based power control and between the bunches we use time/frequency hopping to average the interference. We propose an improved RRM algorithm and evaluate the performance of the bunch concept for a Manhattan scenario with mixed traffic. The performance is improved while the computational complexity is reduced compared to our previously published results for the bunch concept. We also show that the performance of a single bunch system is close to the theoretical upper bound.
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  • Berg, Miguel (författare)
  • Maintaining high Capacity for Centralized DCA with Limited Measurements and Signaling
  • 1999
  • Ingår i: Proceedings of the 1999 10th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC '99, Osaka, Japan, Sept 12 - 15, 1999. - New York : IEEE.
  • Konferensbidrag (refereegranskat)abstract
    • Centralized dynamic channel allocation strategies can, in theory, achieve very high capacity in terms of achievable load at a certain quality level. Unfortunately, these strategies have often been considered non-feasible in practice due to the massive amount of measurements and signaling typically required. In this paper we evaluate some methods to maintain high performance while drastically reducing the measurement and signaling requirements. Our DCA algorithm is based on measurements of the link gain matrix. We show that for a microcellular Manhattan environment, only the gains from the three strongest beacons have to be measured and signaled by each mobile in order to achieve almost the same capacity as an ideal system where all beacons can be measured.
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  • Berglund, P., et al. (författare)
  • Alcohols as enantioselective inhibitors in a lipase catalysed esterification of a chiral acyl donor
  • 1995
  • Ingår i: Biotechnology Letters. - 0141-5492. ; 17:1, s. 55-60
  • Tidskriftsartikel (refereegranskat)abstract
    • Increased reaction rates and increased enantioselectivities were observed with decreased concentrations of n-alkanols when resolving 2-methyldecanoic acid by esterification catalysed by immobilised lipase from Candida rugosa at controlled water activities in cyclohexane. The enantioselectivity was found to be independent of the water activity in the reaction medium at the n-heptanol concentrations investigated. However, when n-decanol was used as the acyl acceptor, not only the alcohol concentration but also the water activity in the reaction medium, influenced the enantioselectivity. The results obtained showed that the low enantioselectivity seen at a high alcohol concentration could be explained by the alcohol influencing the apparent V(max)(S) and V(max)(R) differently.
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  • Eriksson, Magnus, et al. (författare)
  • Dynamic Radio Resource Management Schemes for Interactive Services in DVB-T and DAB
  • 1999
  • Ingår i: Proceedings of Radiovetenskap och kommunikation. - Karlskrona : Högskolan i Karlskrona/Ronneby. - 9163081563
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The topic of this paper is dynamic schemes for downlink packet radio resource management. The results can be applied to personal communication services in the terrestrial digital video and audio broadcasting systems (DVB-T and DAB). Dynamic single frequency networks (DSFN) are investigated, meaning that the macro diversity capability of the COFDM modulation scheme is utilised for cellular communication. The concept of PARPS (Packet and Resource Plan Scheduling) is introduced. PARPS reduces the combined problem of dynamic radio resource management, including DSFN, dynamic channel allocation, power control, link adaptation, etc, to a scheduling problem. We propose several optimised and heuristic PARPS schemes. Our results show that some of the heuristic schemes have near-optimal delay performance. We also have results indicating that the capacity of the PARPS schemes for 2D Poisson traffic can be evaluated with static analyses, i.e. without simulation of a queuing system.
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  • Eriksson, Magnus, et al. (författare)
  • The Concepts of PARPS : Packet and Resource Plan Scheduling
  • 1999
  • Ingår i: Multiaccess, Mobility and Teletraffic for Wireless Communications (MMT '99), Venice, Italy, October 6-8, 1999.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Dynamic schemes for downlink packet radio resource management (RRM) are the topic of this paper. The concept of PARPS (Packet And Resource Plan Scheduling) is introduced. PARPS reduces the combined proble m of dynamic RRM, including statistical multiplex, dynamic channel allocation, power control, link adaptation, reuse partitioning, soft handover, admission control, etc, to a scheduling problem. PARPS makes it possible to achieve dynamic RRM individually for each data packet, without performing signal-to-interference ratio calculations for every single packet. A PARPS algorithm assigns a so-called resource plan to each timeslot, and assigns data packets to timeslots and transmitters. A resource plan is a combination of several radio parameters, e.g. transmitter power levels, coding rates and modulation schemes, for a group of centrally controlled and synchronised transmitters. We propose several optimised and heuristic PARPS algorithms. Optimised PARPS is NP hard, i.e. it is not realistic to solve in real time for a big system, but it can be used for finding an upper bound for the compound effect of several RRM techniques by means of computer simulations. The heuristic algorithms are realistic to implement in real systems. Our results show that some of the heuristic algorithms have delay performance very near an optimised algorithm, and that the capacity and coverage of a set of resource plans for 2D Poisson traffic can be evaluated with static analyses, i.e. without queuing system simulation. We apply PARPS to cellular systems based on the COFDM modulation scheme. Especially, we have personal communication services in the MEMO system in mind, where the terrestrial digital audio or video broadcasting system (DAB or DVB-T) is used as a broadband downlink, in combination with some narrowband uplink, e.g. GSM.
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  • Resultat 1-10 av 19

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