WiMAX is a wide-area wireless standard in which base stations send radio waves over a large area to provide high-speed data communication.
WiMAX targets areas the size of a whole town, so in the split between LAN and WAN it falls on the wide-area side. User devices link to a base station by radio, which means they can reach the internet without any cabling work and can also be used on the move.
How to rememberThe name is an acronym of Worldwide Interoperability for Microwave Access, showing that it is a way of connecting (Access) by microwaves (Microwave).
Exam points
Mix-upWiMAX sounds like Wi-Fi, but it is a wide-area wireless standard, not a wireless LAN (無線LAN) for use inside a building or site.
LTE is a mobile standard for high-speed data communication over the base station network of mobile phones, generally treated as the representative fourth-generation (4G) method.
It was introduced as networks moved on from 3G, and it sends data faster than 3G. LTE became the foundation for data on smartphones and similar devices, and the generation after it is 5G.
AnalogyLike widening a road built for phone calls into a highway that moves large loads quickly.
How to rememberLong Term Evolution: the name marks it as one stage in a long evolution that started from 3G.
Exam points
ExamLTE is a standard used on mobile phone networks (携帯電話網), offering faster data communication than 3G.
5G is the fifth-generation mobile communication system that follows LTE (4G); besides high speed and large capacity, it features low latency and massive simultaneous connections.
Latency (遅延) is the wait between sending data and its arrival at the other end, and a network with little of it suits uses that need an instant response, such as remote operation. A single base station area can also connect huge numbers of devices at once, so 5G is expected to serve as the communication base for IoT systems that use many sensors.
AnalogyLike a road with many more lanes, short waits at merges, and room for an enormous number of cars at once.
How to rememberThe G stands for Generation, not Giga. 5G simply means "fifth generation."
Exam points
Exam5G is a mobile communication system with higher speed and capacity (高速大容量) than LTE, plus low latency (低遅延) and massive simultaneous connections (多数同時接続).
Mix-up5G names a generation of communication method, a different axis from the form an operator takes. Operators with their own equipment and MVNOs that lease other companies' lines can both offer service over 5G.
ExamFor IoT devices there is also LPWA besides 5G, a wireless approach that communicates over a wide area on little power.
Transmission speed (伝送速度) measures how fast a line communicates by the amount of data it can send per second, using the unit bps.
Convert to bits: 600 MB × 8 = 4800 Mbit
Effective speed: 40 Mbps × 0.5 = 20 Mbps
Transfer time: 4800 ÷ 20 = 240 s
Divide the data size in bits by the effective speed to get the transfer time in seconds.
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The time to finish sending data is found as data size ÷ transmission speed. On a real line, overhead such as control information keeps the speed below its rated value, so you multiply by the usable share, the transmission efficiency (伝送効率), and calculate with the resulting effective speed (実効速度).
AnalogyLike the amount of water a pipe can carry each second. The wider the pipe, the sooner the same amount of water gets through.
How to rememberSame shape as distance = speed × time: data size = transmission speed × time. To find the time, divide.
Exam points
ExamTo get the transfer time, convert the data size to bits and divide by the effective speed (実効速度), which is the transmission speed (伝送速度) times the transmission efficiency (伝送効率). Dropping the ×8 from bytes to bits makes the answer one eighth of the correct value.
ExamCongestion (輻輳) is the state in which usage piles up at once beyond what the network can handle, so communication stalls.
ExamOn a wireless LAN (無線LAN), radio interference (干渉) from other nearby wireless equipment lowers the speed or makes the connection unstable.
bps stands for bits per second, a unit that expresses transmission speed as the number of bits sent per second.
Real line speeds are large numbers, so prefixed forms such as kbps and Mbps are common, using k (10^3), M (10^6), and G (10^9). File sizes are usually given in bytes (B), and since 1 byte = 8 bits, the units must match before you combine them with bps.
How to rememberLowercase b means bit and uppercase B means byte, so "Mbps" and "MB/s" are different amounts.
Exam points
ExamThe unit for communication speed on a network is bps, the number of bits per second.
Mix-upTransmission speed (伝送速度) is the name of a quantity, speed, while bps is the unit that puts a number on that quantity.