Millimeter-wave Wireless LAN and its Extension toward 5G Heterogeneous Networks

Millimeter-wave (mmw) frequency bands, especially 60 GHz unlicensed band, are considered as a promising solution for gigabit short range wireless communication systems. IEEE standard 802.11ad, also known as WiGig, is standardized for the usage of the 60 GHz unlicensed band for wireless local area networks (WLANs). By using this mmw WLAN, multi-Gbps rate can be achieved to support bandwidth-intensive multimedia applications. Exhaustive search along with beamforming (BF) is usually used to overcome 60 GHz channel propagation loss and accomplish data transmissions in such mmw WLANs. Because of its short range transmission with a high susceptibility to path blocking, multiple number of mmw access points (APs) should be used to fully cover a typical target environment for future high capacity multi-Gbps WLANs. Therefore, coordination among mmw APs is highly needed to overcome packet collisions resulting from un-coordinated exhaustive search BF and to increase the total capacity of mmw WLANs. In this paper, we firstly give the current status of mmw WLANs with our developed WiGig AP prototype. Then, we highlight the great need for coordinated transmissions among mmw APs as a key enabler for future high capacity mmw WLANs. Two different types of coordinated mmw WLAN architecture are introduced. One is the distributed antenna type architecture to realize centralized coordination, while the other is an autonomous coordination with the assistance of legacy Wi-Fi signaling. Moreover, two heterogeneous network (HetNet) architectures are also introduced to efficiently extend the coordinated mmw WLANs to be used for future 5th Generation (5G) cellular networks.Comment: 18 pages, 24 figures, accepted, invited paper

実物大斜面落石実験によるジオグリッドとジオセルを用いた補強土壁の評価

金沢大学理工研究域環境デザイン学系Full-scale slope-rockfall tests were carried out in order to confirm the rockfall protection performance of soil-walls reinforced with two alternating kinds of geogrids. Moreover, cushioning layers made of geocells filled with relatively small gravel were arranged on the upstream side of reinforced soil-walls to buffer and disperse the impact of rockfalls. The reinforced soil-walls were demonstrated to have excellent performance as rockfall protection structures. Advanced techniques to measure the impact force of rockfalls rolling down actual slopes and design essentials of reinforced soil-walls were also developed.現在，落石の危険を伴う斜面に用いる対策は多種多様な工種があるが，補強土壁は落石防護構造として効果的であることが最近の研究でわかってきた．著者らは，ジオグリッドによる補強土壁における落石防護性能の確認を目的として，斜面落石に対する実物大実験を実施した．また，単粒度砕石を充填したジオセルを補強土壁の山側に配置し，落石の衝撃に対する緩衝効果を検証した．本研究では，補強土壁は落石防護性能に優れるとともに，ジオセルによる緩衝体は落石の衝撃緩和に効果的であるとの評価を得た．本論文では，実験方法および実験結果について考察し報告する