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RISS 인기검색어
- 검색키워드
- 저자 : Molisch, Andreas F. (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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Karttunen, Aki,Molisch, Andreas F.,Hur, Sooyoung,Park, Jeongho,Zhang, Charlie Jianzhong IEEE 2017 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.16 No.11
<P>This paper considers a fundamental issue of path loss (PL) modeling in urban micro cell (UMi) environments, namely the spatial consistency of the model as the mobile station moves along a trajectory through street canyons. This paper is motivated by the observed non-stationarity of the PL. We show that the traditional model of power law PL plus log-normally distributed variations can provide misleading results that can have serious implications for system simulations. Rather, the PL parameters have to be modeled as random variables that change from street to street and also as a function of the street orientation. Variations of the PL, taken over the ensemble of the whole cell (or multiple cells), thus consist of the compound effect of these PL parameter variations together with the traditional shadowing variations along the trajectory of movement. Ray-tracing results demonstrate that ignoring this effect can lead to a severe overestimation of the local standard deviation in a given area. Then, a spatially consistent stochastic street-by-street PL model is established, and a parameterization for 28-GHz UMi cells is given. The model correctly describes the PL as a function of the street orientation as well as the large variance observed for all the PL model parameters.</P>
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Fast Millimeter-Wave Beam Training with Receive Beamforming
김중헌,Andreas F. Molisch 한국통신학회 2014 Journal of communications and networks Vol.16 No.5
This paper proposes fast millimeter-wave (mm-wave)beam training protocols with receive beamforming. Both IEEEstandards and the academic literature have generally consideredbeam training protocols involving exhaustive search over all possiblebeam directions for both the beamforming initiator and responder. However, this operation requires a long time (and thus overhead)when the beamwidth is quite narrow such as for mm-wavebeams (1 in the worst case). To alleviate this problem, we proposetwo types of adaptive beam training protocols for fixed and adaptivemodulation, respectively, which take into account the uniquepropagation characteristics of millimeter waves. For fixed modulation,the proposed protocol allows for interactive beam training,stopping the search when a local maximum of the power angularspectrum is found that is sufficient to support the chosen modulation/coding scheme. We furthermore suggest approaches to prioritizecertain directions determined from the propagation geometry,long-termstatistics, etc. For adaptive modulation, the proposedprotocol uses iterative multi-level beam training concepts for fastlink configuration that provide an exhaustive search with signifi-cantly lower complexity. Our simulation results verify that the proposedprotocol performs better than traditional exhaustive searchin terms of the link configuration speed for mobile wireless serviceapplications.
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On Millimeter Wave and THz Mobile Radio Channel for Smart Rail Mobility
Guan, Ke,Li, Guangkai,Kurner, Thomas,Molisch, Andreas F.,Peng, Bile,He, Ruisi,Hui, Bing,Kim, Junhyeong,Zhong, Zhangdui IEEE 2017 IEEE Transactions on Vehicular Technology VT Vol.66 No.7
<P>As a widely acknowledged efficient and green transportation model, rail traffic is expected to evolve into a new era of 'smart rail mobility' whereby infrastructure, trains, and travelers will be interconnected to achieve optimized mobility, higher safety, and lower costs. Thus, a seamless high-data rate wireless connectivity with up to dozens of gigahertz bandwidth is required. Such a huge bandwidth requirement motivates the exploration of the underutilized millimeter (mm) wave and terahertz (THz) bands. In this paper, the motivations for developing millimeter wave and THz communications for railway are clarified by first defining the applications and scenarios required for smart rail mobility. Ray-tracing simulations at 100 GHz imply that to form high-gain directional antenna beams, dynamic beamforming strategies and advanced handover design are critical for the feasibility of THz communications to enable smart rail mobility.</P>
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Ko, Junghoon,Cho, Yeon-Jea,Hur, Sooyoung,Kim, Taehwan,Park, Jeongho,Molisch, Andreas F.,Haneda, Katsuyuki,Peter, Michael,Park, Dong-Jo,Cho, Dong-Ho IEEE 2017 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.16 No.9
<P>The millimeter-wave (mm-wave) band will be a key component of fifth-generation (5G) wireless communication systems. This paper presents radio propagation measurements and analysis investigating the wideband directional channel characteristics of the mm-wave transmission for in-building and urban cellular communication systems in the 28-GHz band. Based on the measurements, we analyze and model the spatio-temporal channel characteristics such as multipath delay, angular statistics, and path loss. In particular we investigate the clustering of the multipath components, and investigate both the intracluster and inter-cluster distributions. Based on these investigations, we present a complete channel model suitable for system simulations in the in-building and urban environments.</P>
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Wireless Multihop Device-to-Device Caching Networks
Jeon, Sang-Woon,Hong, Song-Nam,Ji, Mingyue,Caire, Giuseppe,Molisch, Andreas F. IEEE 2017 IEEE transactions on information theory Vol.63 No.3
<P>We consider a wireless device-to-device network, where n nodes are uniformly distributed at random over the network area. We let each node caches M files from a library of size m >= M. Each node in the network requests a file from the library independently at random, according to a popularity distribution, and is served by other nodes having the requested file in their local cache via (possibly) multihop transmissions. Under the classical 'protocol model' of wireless networks, we characterize the optimal per-node capacity scaling law for a broad class of heavy-tailed popularity distributions, including Zipf distributions with exponent less than one. In the parameter regime of interest, i.e., m = o(nM), we show that a decentralized random caching strategy with uniform probability over the library yields the optimal per-node capacity scaling of Theta(root M/m) for heavy-tailed popularity distributions. This scaling is constant with n, thus yielding throughput scalability with the network size. Furthermore, the multihop capacity scaling can be significantly better than for the case of single-hop caching networks, for which the per-node capacity is Theta(M/m). The multihop capacity scaling law can be further improved for a Zipf distribution with exponent larger than some threshold >1, by using a decentralized random caching uniformly across a subset of most popular files in the library. Namely, ignoring a subset of less popular files (i.e., effectively reducing the size of the library) can significantly improve the throughput scaling while guaranteeing that all nodes will be served with high probability as n increases.</P>
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