An IoT area network (IoTエリアネットワーク) links IoT devices such as sensors within a limited space like a factory or a home, and connects them through an IoT gateway to the wide-area network and IoT servers outside.
IoT devices (sensors, etc.)
IoT area network (wireless / wired)
IoT gateway
Wide-area network
IoT server
The IoT gateway is the entry and exit point between traffic inside the area and the wide-area network outside, relaying data and converting its format. Inside the area, devices connect by short-range wireless such as ZigBee, and also by PLC, a wired method that uses the power lines carrying electricity as the communication path. With multi-hop (マルチホップ) relaying, where one device picks up another's signal and passes it on again and again, the network covers a wider area than any single device's signal can reach.
AnalogyThink of an apartment building: the rooms (devices) are joined by the building's wiring or wireless, and everyone goes in and out to the street through the front entrance (the gateway).
How to rememberThe "gate" in gateway is literally a gate: the one that separates the inside of the area from the outside.
Exam points
ExamAn IoT area network can be built with wires as well as wireless. PLC, for example, uses power lines as its communication path and counts as a wired method.
ExamMulti-hop (マルチホップ) extends coverage by having devices relay signals for one another again and again, and IoT area networks use it too.
LPWA (Low Power Wide Area) is an umbrella term for IoT wireless methods that combine low power with wide coverage, at the cost of low data rates.
When a device only sends small readings such as temperatures or meter values, a low data rate rarely gets in the way. A battery alone keeps it running for years and its signal reaches several to tens of kilometers, so it suits collecting data from devices scattered over a large region.
AnalogyIt is like a mail carrier who cannot haul big parcels but keeps delivering letters to distant villages on almost no fuel.
How to rememberThe name holds only Low Power and Wide Area; no word in it says anything about speed.
Exam points
ExamLPWA puts power and reach ahead of speed. It is therefore slower than wireless LAN (無線LAN) and mobile phone networks, but it draws less power than wireless LAN.
ExamLPWA reaches far beyond short-range wireless LAN. It uses less power not only than wireless LAN but also than fourth-generation mobile networks (4G).
BLE (Bluetooth Low Energy) is a low-power, short-range wireless specification added to Bluetooth.
It arrived with Bluetooth 4.0 and draws so little power that an ordinary coin cell keeps it going for a long time. It suits sensors and wearables that send small amounts of data now and then.
AnalogyRather than talking loudly all the time, it is like murmuring a quick word to the person beside you only when there is something to say.
How to rememberLE stands for Low Energy, so the name reads as "the energy-saving Bluetooth".
Exam points
ExamBLE keeps its power use low by sending small amounts of data in short bursts and resting in between, so it can keep running for a long time even on a coin cell.
ExamBLE links IoT devices to a nearby IoT gateway (IoTゲートウェイ) on little power, and it is also used to gauge the distance between the sending and receiving devices.
Mix-upBLE and LPWA both save power, but BLE is a short-range part of the Bluetooth spec, while LPWA is an umbrella term for wide-area methods that reach several kilometers or more.
A beacon (ビーコン) is a small device that keeps sending its own ID signal at fixed intervals, giving a receiving device a clue that it is near the beacon and where it is.
Beacon (transmitter)
Receiver such as a smartphone
App shows information
An app shows guidance or information that fits where the device is.
3 / 3
Most beacons transmit over BLE and run for a long time on a battery. The receiver, such as a smartphone, estimates how far away the transmitter is from the signal strength and uses an app to show information suited to that spot. Even inside buildings where satellite signals barely reach, the places where transmitters are installed serve as landmarks for finding where you are.
AnalogyIt resembles a lighthouse flashing at a steady rhythm over the night sea, letting ships that see it work out their position.
How to rememberThe English word beacon first meant a signal fire or lighthouse lamp: a marker that sends a sign far away.
Exam points
Mix-upThe beacon only sends the ID signal; it is the receiving device that estimates distance and location.
Edge computing (エッジコンピューティング) places computers close to the IoT devices to process data there, then sends the results on to the IoT server.
Process everything at the server
Process at the edge, then send
Where processing happens
A distant IoT server
A computer near the IoT devices
Data flowing over the network
Large: all raw data is sent
Small: data is filtered first
Time to respond
Long: waits for a round trip to the server
Short: decisions are made on site
Server load
Grows as devices are added
Lighter: the site takes on part of the work
Because processing happens near the site, the system can respond without waiting for a round trip to a distant server, which suits control tasks that need an immediate (real-time) response. Filtering data before sending it also cuts network traffic and the load on the server.
AnalogyInstead of checking everything with head office, each branch settles what it can decide itself and reports only the outcome to head office.
How to rememberEdge means the rim or border: seen from the server at the network's center, the edge is the on-site side, and that is where processing happens.
Exam points
ExamEdge computing hands processing to computers placed beside the IoT devices, lowering the IoT server's load and improving real-time response (リアルタイム性).
ExamPulling out only the needed part of the data on site and sending the reduced amount to the server also counts as edge computing.
Mix-upCompared by where processing happens, cloud computing (クラウドコンピューティング) gathers it in a distant data center, while edge computing keeps it on site, where the IoT devices are.