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  • 1.
    Apelfröjd, Rikke
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Design and measurement based evaluations of coherent JT CoMP: A study of precoding, user grouping and resource allocation using predicted CSI2014Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Artikel i tidskrift (Refereegranskat)
  • 2.
    Apelfröjd, Rikke
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Design and measurement based evaluations of coherent JT CoMP: a study of precoding, user grouping and resource allocation using predicted CSI2014Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, s. 100-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coordinated multipoint (CoMP) transmission provides high theoretic gains in spectral efficiency with coherent joint transmission (JT) to multiple users. However, this requires accurate channel state information at the transmitter (CSIT) and also user groups with spatially compatible users. The aim of this paper is to use measured channels to investigate if significant CoMP gains can still be obtained with channel estimation errors. This turns out to be the case, but requires the combination of several techniques. We here focus on coherent downlink JT CoMP to multiple users within a cluster of cooperating base stations. The use of Kalman predictors is investigated to estimate the complex channel gains at the moment of transmission. It is shown that this can provide sufficient CSIT quality for JT CoMP even for long (> 20 ms) system delays at 2.66 GHz at pedestrian velocities or, for lower delays, at 500 MHz, at vehicular velocities. A user grouping and resource allocation scheme that provides appropriate groups for CoMP is also suggested. It provides performance close to that obtained by exhaustive search at very low complexity, low feedback cost and very low backhaul cost. Finally, a robust linear precoder that takes channel uncertainties into account when designing the precoding matrix is considered. We show that, in challenging scenarios, this provides large gains compared with zero-forcing precoding. Evaluations of these design elements are based on measured channels with realistic noise and intercluster interference assumptions. These show that high JT CoMP gains can be expected, on average over large sets of user positions, when the above techniques are combined - especially in severely intracluster interference limited scenarios.

  • 3.
    Jacobsson, Martin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Comparing wireless flooding protocols using trace-based simulations2013Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, s. 169:1-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most wireless multi-hop networks, such as ad hoc networks and wireless sensor networks, need network-wide broadcasting, which is best done with a flooding protocol. In this article, we use packet trace information from a real test-bed network to define a simulator for flooding protocol performance studies. Five protocols are compared using the simulator. Trace-based simulations promise to have the benefits of the simulator, such as reducing required work effort and repeatability but still produce results close to the real test-bed or deployment. We propose and evaluate different approaches on how to use collected trace data and how to tune the parameters to achieve the best possible accuracy in comparison with actual test-bed measurements. We study the resulting accuracy of the model so that performance studies know with what confidence a certain conclusion can be made. Using the new trace-based model and knowing its accuracy, we compare the five flooding protocols to gain additional insights into their performance. Finally, by modifying the trace data, we study how real-world effects, such as links with in-between qualities and asymmetric links, influence the different flooding protocols.

  • 4. Limmanee, A
    et al.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Nekouei, E
    Optimal power policies and throughput scaling analyses in fading cognitive broadcast channels with primary outage probability constraint2014Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, s. 35-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper focuses on a spectrum-sharing-based fading cognitive radio broadcast channel (BC) with a single-antenna secondary base station (SBS) and M single-antenna secondary receivers (SRs) utilizing the same spectrum band with a delay-sensitive primary user (PU). The service-quality requirement for the primary user is set by an outage probability constraint (POC). We address the optimal power allocation problem for the SBS ergodic sum capacity (ESC) maximization in the secondary BC network subject to POC and a transmit power constraint at SBS specified by either a long-term or a short-term power constraint. The optimality conditions reveal that in each joint channel state, the SBS allocates transmission power to the only one selected SR with the highest value of a certain metric consisting of the ratio of the SR's direct channel power gain and the sum of interference power and noise power at the SR. Then, the secondary network throughput scaling analysis as the number of SRs becomes large, is also investigated, showing that if PU applies a truncated channel inversion (TCI) power policy, the SBS ESC scales like epsilon(p) log(log M) where epsilon(p) is the PU outage probability threshold. To reduce the amount of channel side information (CSI) transferred between the two networks, we propose a suboptimal transmission scheme which requires only 1-bit feedback from the delay-sensitive PR (partial CSI). We show that the new power control policy is asymptotically optimal, i.e. the SBS ESC under this reduced feedback scheme still scales like epsilon(p) log(log M).

  • 5. Liu, Jiangchuan
    et al.
    Cao, Jiannong
    Li, Xiang-Yang
    Sun, Limin
    Wang, Dan
    Ngai, Edith C.-H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Design, Implementation, and Evaluation of Wireless Sensor Network Systems2010Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, s. 439890:1-2Artikel, forskningsöversikt (Övrigt vetenskapligt)
  • 6.
    Svensson, Tommy
    et al.
    Chalmers University of Technology, Dept of Signals and Systems.
    Frank, Tobias
    Communications Engineering Laboratory, Technische Universität Darmstadt, DE-64283 Darmstadt, Germany.
    Eriksson, Thomas
    Dept of Signals and Systems, Chalmers University of Technology, Göteborg.
    Aronsson, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Klein, Anja
    Communications Engineering Laboratory, Technische Universität Darmstadt, DE-64283 Darmstadt, Germany.
    Block interleaved frequency division multiple access for power efficiency, robustness, flexibility and scalability2009Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2009, s. 720973-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The multiple access solution in an IMT-Advanced mobile radio system has   to meet challenging requirements such as high throughput, low delays,   high flexibility, good robustness, low computational complexity, and a   high power efficiency, especially in the uplink. In this paper, a novel   multiple access scheme for uplinks denoted as B-IFDMA is presented. We   show that this scheme is able to provide equal or better error rate   performance than the Single-Carrier Frequency Division Multiple Access   (SCFDMA) schemes IFDMA and LFDMA, when considering realistic channel   estimation performance at the receiver and no reliable channel state   information at the transmitter. We also show that B-IFDMA provides   better amplifier efficiency than OFDMA and can provide better   end-to-end energy efficiency than IFDMA and LFDMA. Moreover, the scheme   shows a promisingly high robustness to frequency-offsets and Doppler   spread. Thus, this scheme can be regarded as a promising solution for   the uplink of future mobile radio systems.

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