Wired and Wireless Communication, GSM, and 3G to 6G

Wired and wireless compared

Wired — twisted pair, coaxial cable, optical fibre. The signal is guided along a physical path.

Wireless — the signal radiates through free space as an electromagnetic wave.

The honest summary: wired wins on capacity and reliability, wireless wins on mobility, and no amount of engineering changes that trade-off. Real networks are hybrids — a mobile call travels wirelessly only as far as the nearest tower, and goes the remaining distance over fibre.

GSM

Global System for Mobile communications — the second-generation digital standard, and still the architecture underlying later generations.

Block diagram, in three subsystems:

1. Mobile Station (MS)

• Mobile Equipment — the handset itself
• SIM — Subscriber Identity Module, holding subscriber identity independently of the handset

2. Base Station Subsystem (BSS)

• BTS, Base Transceiver Station — the radio equipment of one cell
• BSC, Base Station Controller — manages several BTSs, handles handover between them and allocates radio channels

3. Network and Switching Subsystem (NSS)

• MSC, Mobile Switching Centre — the switching core, connecting calls and interfacing to the fixed telephone network
• HLR, Home Location Register — the permanent database of subscribers
• VLR, Visitor Location Register — a temporary record of subscribers currently in this MSC's area
• AUC, Authentication Centre — security keys
• EIR, Equipment Identity Register — a register of handset identities, used to bar stolen phones

The two ideas worth understanding.

The cell. Coverage is divided into cells, each with its own BTS at low power. Because power is low, the same frequency can be reused in another cell far enough away. Capacity is therefore set by how small the cells are, not by how much spectrum exists — which is why urban networks add capacity by adding cells rather than by finding new frequencies.

The SIM. Separating subscriber identity from the handset was a genuine innovation. It made phones portable between networks and subscriptions portable between phones, and it is why the industry developed as it did.

Generations compared

What actually changed at each step, which is the more useful way to hold it than the numbers:

• 3G made data a first-class service rather than an add-on to voice.
• 4G abandoned circuit switching entirely for all-IP, and made streaming video the normal use of a phone.
• 5G is less about raw speed than about latency and density: a millisecond of delay makes remote control and vehicle-to-vehicle communication feasible, and the standard supports about a million devices per square kilometre for IoT.
• 6G remains a research programme, not a deployed standard. Targets include terahertz frequencies, integrated sensing and communication, and AI built into the network rather than layered on top.

A caution worth carrying. Higher frequencies buy bandwidth but lose range and penetration: millimetre waves are blocked by walls, foliage and rain, which is why 5G needs far more base stations than 4G and why its rollout has been slower and costlier than the headline speeds suggest. Any claim about 6G should be read as a target rather than an achievement.