Recently, the products which Bluetooth is commonly used are becoming popular also with the mouse / keyboard / earphone and us familiar. And, as can be seen from these products, the application of Bluetooth is short-distance wireless communication, in short, the communication distance is classified into three classes in proportion to the radio wave strength. The breakdown is “Class 1” 1 m, “Class 2” 10 m, “Class 3” 100 m, and can only communicate up to about 100 m at maximum.

次に帯域ですが、ISM(Industry Science Medical:産業科学医療用)バンドという無免許の2.4GHz帯の電波が利用されています。これは、我々が日頃お世話になっているWiFiと同じ帯域です。「それならば、通信距離が長いWiFiの方がいいのでは?」と思う方もいるかもしれませんが、勿論Bluetoothにも良いところはあります。

 Next band is the radio of the unlicensed 2.4 GHz band called ISM (Industry Science Medical) band is used. This is the same band as WiFi that we are indebted with. Although it may be that some people think that WiFi with long communication distance is better if it is so, of course there is also a good place for Bluetooth.

BluetoothとWiFiの大きな違いの一つに、スペクトラム拡散方式の違いがあります。ちなみに、スペクトラム拡散方式とは受信側で信号を復調した際に雑音レベルを小さくでき、他電波との干渉を小さくできる技術のことです。Bluetoothでは周波数ホッピング方式(FHSS/frequency hopping spread spectrumWiFiでは直接スペクトラム拡散方式(DSSS/Direct Sequence Spread Spectrum)が採用されています。また、周波数ホッピング方式は直接スペクトラム拡散方式に比べて回路や制御が単純になっています。もうお気付きかもしれませんが、Bluetoohの利点は省電力であることです。出力する電波強度が小さく、変復調にも単純な回路を用いることで、実現可能となっています。

 One of the big differences between Bluetooth and WiFi is the difference in spread spectrum method. By the way, the spread spectrum method is a technology that makes it possible to reduce the noise level when demodulating the signal on the receiving side and reduce the interference with other radio waves. Bluetooth adopts frequency hopping spread spectrum (FHSS / frequency hopping spread spectrum), and WiFi uses direct spread spectrum method (DSSS / Direct Sequence Spread Spectrum). In addition, the frequency hopping method has simpler circuit and control than the direct spread spectrum method. As you may have noticed, the advantage of Bluetooth is that it is power saving. It is possible to realize by using a simple circuit for modulation / demodulation, because the intensity of the radio wave to be output is small.



まず、現時点で最新規格のBluetooth Low Energyでは、これまでの規格に比べ伝送速度や通信距離こそ前規格に比べて小さくなっているものの(例.伝送速度:2Mbps→最大1Mbps)、電池寿命が「~数カ月」から「~数年間」と大幅に改善しています。必要なとき以外はスリープ状態機能の追加も大きく影響しているでしょう。そしてこれは、今後のIoT市場に向け、センサやウェアラブル端末への展開を考慮しての改善です。センサ1兆個と言われる時代が到来した際に、仮にすべての無線通信にBluetoothが採用されるようなことがあれば、その市場価値は凄いことになりそうですね。これまでの役目は、デスク周りの配線をスッキリさせることでしたが、明るい未来が待っていそうです。

 First of all, at the present time, Bluetooth Low Energy, which is the newest standard, has lower transmission speed and communication distance than previous standards (eg, transmission speed: 2 Mbps → maximum 1 Mbps), battery life is ” From a few months “to” a few years “has greatly improved. The addition of the sleep state function will have a big influence other than when necessary. And this is an improvement in consideration of deployment to sensors and wearable terminals toward future IoT market. If there is a time when it is said that 1 trillion sensors are coming, if there is something like Bluetooth being adopted for all wireless communication, its market value is going to be amazing. The task so far was to make the wiring around the desk clean, but a bright future seems to be waiting.