問96
頻出度★★★
無線 LAN で利用されている周波数帯の2.4 GHz 帯, 5GHz 帯に関する記述として, 適切なものはどれか。
平成30年度 秋期 ITパスポート試験 問96
テクノロジ系ネットワーク › ネットワーク方式
This question's explanation and your answers so far.
解説
問 96
Incorrectア
The 2.4 GHz band and the 5 GHz band occupy different frequency bands, so they do not interfere with each other and can be used at the same time even in the same room. Devices that support both bands (dual-band) actually use them together, so saying they 'cannot be used at the same time' is incorrect.
- イ
正解 The lower a radio wave's frequency (the longer its wavelength), the more easily diffraction occurs that lets the wave bend around obstacles, so it reaches its destination even when there are barriers such as walls. Because the 2.4 GHz band has a lower frequency than the 5 GHz band, it is more resistant to obstacles and its radio waves reach farther more easily. Therefore, choice イ, which states that 'compared with the 5 GHz band, the 2.4 GHz band is more resistant to obstacles and its radio waves reach farther more easily', is appropriate.
Incorrectウ
WPA2 is an encryption standard and has nothing to do with which frequency band is used. Both the 2.4 GHz band and the 5 GHz band support WPA2 encrypted communication, so saying that 'the 5 GHz band does not support it' is incorrect.
Incorrectエ
The direction of the interference is the reverse of reality. The 2.4 GHz band shares the ISM band with microwave ovens, cordless phones, Bluetooth and the like, so it is prone to radio interference from home appliances. The 5 GHz band, by contrast, does not overlap with those appliances and receives almost no appliance-borne interference. The statement that the 2.4 GHz band is not interfered with while the 5 GHz band is, is therefore incorrect.
ここがポイント
- The lower a radio wave's frequency (the longer its wavelength), the more easily it diffracts, so it is more resistant to obstacles and reaches farther. The 2.4 GHz band has a lower frequency than the 5 GHz band, so this property is stronger.
- The 2.4 GHz band is prone to interference with home appliances such as microwave ovens, while the 5 GHz band is fast but weak against obstacles. Encryption such as WPA2 does not depend on the frequency band.
用語