MIMO is a wireless technology that uses multiple antennas at both the sending and receiving ends, moving several streams of data at once to speed up communication.
Split the data
Send from several antennas at once
Receive on several antennas
Restore the original data
The separated streams are joined back together into the original data.
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In Japanese it is read "maimo". Compared with sending in sequence over one antenna, it carries more data at a time without widening the radio bandwidth. Smartphones use it for 4G and 5G, and wireless LANs use it too.
AnalogyWith one service counter, parcels can only be handed over in turn; open more counters and several can change hands at once.
How to rememberThe letters stand for Multiple Input Multiple Output: more than one way in and more than one way out.
Exam points
Mix-upMIMO is a technology for faster wireless links. MIME, spelled much the same, is a standard for handling attachments and similar content in email.
Carrier aggregation (キャリアアグリゲーション) combines radio waves from several frequency bands (周波数帯) and uses them together, making wireless communication faster and more stable.
Bands combined (example: 20 MHz each)
Total usable bandwidth
Approximate capacity
1
20 MHz
1x
2
40 MHz
2x
3
60 MHz
3x
It is also abbreviated CA. Each added band widens the usable bandwidth, so more data can flow. When the signal in one band is weak, another band can make up for it.
AnalogyPicture traffic that used a single one-lane road now flowing along neighboring parallel roads at the same time.
How to rememberHere "carrier" means not a phone company but the radio wave that carries data (a carrier wave), and "aggregation" means gathering together.
Exam points
ExamCarrier aggregation (キャリアアグリゲーション) is a different technology from handover (ハンドオーバ), which moves a connection from one base station to another.
Mix-upMIMO adds antennas, while carrier aggregation adds frequency bands (周波数帯).
Tethering (テザリング) shares the mobile phone line (携帯電話回線) of a smartphone or similar device with other equipment such as a PC, connecting it to the internet.
PC, etc.
Smartphone (as router)
Base station
Internet
Because the smartphone acts as the relay, a PC can get online while you are out without any dedicated hardware. The two can be linked by, for example, wireless LAN, a USB cable, or Bluetooth.
How to rememberThe English word "tether" means to tie with a rope, which fits the image of a device hitched to a smartphone and led along.
Exam points
ExamDuring tethering (テザリング) the smartphone works as a router (ルータ), so there is no need to buy a separate one for the PC.
ExamThere is more than one way to link the PC, and tethering calls for no special protocol (プロトコル).
ExamGoing through a mobile phone line (携帯電話回線) does not let you skip antivirus protection (ウイルス対策) on the PC.
A SIM card (SIMカード) is a small IC card that stores contract information (契約情報) such as the phone number and subscriber identity, and it goes into a device such as a smartphone.
Insert the card
Device reads the contract info
Carrier checks the contract
Line is ready
Once that check is done, calls and data communication become available.
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The line contract is tied to the information recorded on the card. Move the card to another compatible device, and it communicates under the same contract.
AnalogyThink of a membership card: show it at the shop and the staff can tell which member you are.
How to rememberThe S stands for Subscriber, so you can read the name as "the card that tells subscribers apart".
Exam points
ExamA SIM card (SIMカード) holds contract information and is issued by the mobile carrier.
Mix-upA SIM card identifies a contract. Memory cards (メモリカード) such as SD cards (SDカード), which store music and photos, serve a different purpose.
MNP (Mobile Number Portability) is a scheme that lets you move to another mobile carrier without changing your phone number.
Your contract and SIM switch to the new carrier, but the phone number carries over. With no need to tell everyone a new number, choosing a carrier gets easier.
AnalogyIt is like moving house and hanging the same nameplate on your new door.
How to rememberIt is short for Mobile Number Portability, and "portability" means being able to take something with you.
Exam points
Mix-upMNP is a scheme for taking your number with you. A provider that rents another company's facilities to offer mobile communication (移動体通信) services, such as mobile phone service, is called an MVNO.
An eSIM is a SIM that works by writing contract information to a chip built into the device, so no card has to be inserted or removed.
The contract information is downloaded over the network and written to the chip. There is no waiting for a card, so you can start or switch a line right on the device in your hand.
AnalogyLike replacing the paper membership card in your wallet with one in a smartphone app.
How to rememberThe e stands for embedded.
Exam points
Mix-upAn eSIM is also a kind of SIM for identifying the subscriber; what differs from a SIM card (SIMカード) is the form of its container.
Telematics (テレマティクス) links equipment in cars and other moving vehicles with communication networks and information systems to bring information services to drivers and others.
Car sensors capture conditions
Data is sent over the network to an information system
The system processes it
Driver sees the result
The result appears on the car's display, reaching the driver.
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Services built on telematics include route guidance around traffic jams, automatic emergency calls after an accident, and car insurance priced by distance driven. Each one depends on communication between the car's equipment and an outside information system.
AnalogyImagine a phone operator riding along in the car, on the line to an information center outside.
How to rememberThe word is a blend of telecommunication and informatics (information processing).
Exam points
ExamWhat marks telematics (テレマティクス) is that sensors (センサ) and screens on a moving vehicle (移動体) connect to information systems over a network.
Mix-upA smart meter (スマートメータ) reports electricity and other usage over a network; unlike telematics, it is not aimed at moving vehicles.