5Gの無線の話
ソフトバンクがEricssonを選んだり、イギリスでBTがHuaweiを選んだりと、いよいよインフラ構築が本格化する5Gだが、そもそも何が違うんだっけということで幾つか読んでみた。
Fortunately, at higher frequencies, there is generally a significantly larger bandwidth available to transmit data. Higher bandwidths allow you to modulate the signal more rapidly, which means you can send data quicker – and as technology advances and the richness of applications increase, faster speed is something that almost everyone needs.
周波数を高くすると、帯域幅も広くなる。そして変調が早くなり、データを早く送れる。技術が進歩し、アプリケーションがリッチになり、より高速なデータが求められる。
Higher frequencies have the added benefit that they require smaller antennas (because antenna size needs to be on the order of the wavelength, and as frequency increases, wavelength decreases). This is a significant benefit for miniaturization. Therefore, operating at a higher frequency provides two benefits: often more bandwidth available leading to faster transmission speeds, and smaller antennas leading to smaller devices.
周波数が高くなるとアンテナを小さくできるという利点もある。
But there’s a big trade-off: As frequency increases, the capability of the signal to penetrate into buildings decreases. A cellular or mobile signal that comes in clearly outdoors might be weak once you walk indoors.
ただし、トレードオフもあって、周波数が高くなると信号が建物にpenetrate（入り込む）することができなくなる。建物の中で使いにくいということだ。
Physics, economics, and behavior (of not only people but also apps, devices, processes, etc.) can explain why there are unique networks for IoT (e.g., Zigbee, Thread), why a new high-frequency extension of 5G (called millimeter-wave) may serve the needs of fixed wireless access very well.
なぜZigbeeやThreadといったIoTネットワークがあるか、なぜ5Gの高周波への拡張がfixed wireless accessのニーズに適しているかは、物理特性、経済性、そして人の行動モデルによる。
https://www.networkworld.com/article/3402316/when-to-use-5g-when-to-use-wi-fi-6.html
The architecture for 5G requires many more radio access points and can suffer from poor or no connectivity indoors. So, the typical organization needs to assess its current 4G and potential 5G service for its PCs, routers and other devices. Deploying indoor microcells, repeaters and distributed antennas can help solve indoor 5G service issues.
多くのアクセスポイントが必要で、屋内には届かない。そこで室内のmicrocell、リピーター、分散アンテナが必要になる。
The architecture for 5G makes extensive use of fiber optics to connect the distributed radio access network back to the core of the 5G network. Fiber is typically required to provide the high bandwidth needed to connect 5G endpoints to SaaS-based applications, and to provide live video and high-speed internet access. Private 5G networks will also have to meet high-speed wired-connectivity requirements.
ネットワーク間の接続には光ファイバーが使われる。でも、これって5Gに限らないような。
というわけで、いろいろと消化不良。国内の通信キャリアの情報を読んだほうがしっくりくるかもしれない。
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