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Jihong Park,Seong-Lyun Kim,Zander, Jens IEEE 2016 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.15 No.6
<P>The forthcoming 5G cellular network is expected to overlay millimeter-wave (mmW) transmissions with the incumbent micro-wave (mu W) architecture. The overall mm-mu Wresource management should, therefore, harmonize with each other. This paper aims at maximizing the overall downlink (DL) rate with a minimum uplink (UL) rate constraint, and concludes: mmWtends to focus more on DL transmissions while mu W has high priority for complementing UL, under time-division duplex (TDD) mmW operations. Such UL dedication of mu W results from the limited use of mmW UL bandwidth due to excessive power consumption and/or high peak-to-average power ratio (PAPR) at mobile users. To further relieve this UL bottleneck, we propose mmW UL decoupling that allows each legacy mu Wbase station (BS) to receive mmW signals. Its impact on mm-mu W resource management is provided in a tractable way by virtue of a novel closed-form mm-mu W spectral efficiency (SE) derivation. In an ultra-dense cellular network (UDN), our derivation verifies mmW (or mu W) SE is a logarithmic function of BS-to-user density ratio. This strikingly simple yet practically valid analysis is enabled by exploiting stochastic geometry in conjunction with real three-dimensional (3-D) building blockage statistics in Seoul, South Korea.</P>
Temporal Spectrum Sharing Based on Primary User Activity Prediction
Ki Won Sung,Seong-Lyun Kim,Zander, Jens IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.12
<P>In this paper we investigate the opportunistic spectrum access in temporal domain where a secondary user shares a radio channel with a primary user during the OFF period of the primary user. We consider practical ON/OFF traffic models whose bursty natures are not properly described by a Markovian assumption. An optimal strategy to determine the transmission power of the secondary user is proposed, which can be adapted to any source traffic model of the primary user. This strategy will maximize the spectrum utilization of the secondary user while keeping interference violations to the primary user below a threshold. Numerical results show that the transmission power of the secondary user depends on the probability distribution of the primary traffic as well as the elapsed time of the OFF period.</P>
Scenario making for assessment of secondary spectrum access
Hwang, Youngju,Kim, Seong-Lyun,Sung, Ki, Won,Zander, Jens IEEE 2012 IEEE wireless communications Vol.19 No.4
<P>Secondary spectrum access, through which secondary users opportunistically access the underutilized radio spectrum, has emerged as a solution to cope with the perceived spectrum scarcity. The potential of secondary spectrum has therefore attracted industry players and regulators worldwide. To assess the real-life benefits of the secondary spectrum, it is crucial to estimate the amount of spectrum available for secondary use. This estimation requires a well defined set of models and parameters, which are collectively termed a scenario. In this article, we demonstrate the importance of scenario making in the quantitative assessment of secondary spectrum access. We first describe the elements that constitute a comprehensive secondary access scenario: a primary system and spectrum, a secondary system and usage, and the methods and context of spectrum sharing. Then we demonstrate how the assessment results of the spectrum availability differ depending on the scenario elements. We also illustrate the crucial aspects of a scenario in the business analysis, which, together with the technical assessment, is the input for the regulatory decision.</P>