Wireless and Mobile Communication

Wireless communication carries information through the air as waves, with no connecting cable, allowing people to communicate while on the move. Mobile telephones are the most familiar example. Several technologies and terms are important here.

GSM and CDMA — two mobile technologies. These are two different ways in which mobile phones share the network:

• GSM (Global System for Mobile Communication) is the most widely used mobile standard in the world. It uses a small removable SIM (Subscriber Identity Module) card that stores the user's identity, so a user can move the SIM from one phone to another. It divides each channel by giving users different time slots.
• CDMA (Code Division Multiple Access) lets many users share the same frequency at the same time by giving each call a unique code. In CDMA the user's identity was traditionally tied to the handset rather than a removable SIM.

The practical difference students should note: GSM uses a removable SIM card and is the more common standard, while CDMA identifies users by codes.

WLL — Wireless in Local Loop. WLL is a technology that provides telephone connections to homes and offices using a wireless link instead of the usual copper wire from the exchange to the building (the "local loop"). It is useful where laying cables is difficult or expensive, such as in remote or hilly areas, giving fixed telephone service over a wireless link.

Generations of mobile networks — 1G to 4G and beyond. Mobile networks have improved in "generations," each faster than the last:

• 1G — the earliest, analog networks that carried only voice calls.
• 2G — digital networks (GSM belongs here) that added text messaging (SMS) and basic data.
• 3G (Third Generation) — brought faster mobile data, allowing Internet browsing, e-mail, and video calls on the phone.
• 4G (Fourth Generation) — brought much higher speeds, supporting smooth video streaming, video conferencing, and fast downloads; it is fully data-based.
• 5G, the newest generation, offers still higher speeds and supports many connected devices at once.

Short-range wireless. For connecting devices over short distances we use Bluetooth (linking a phone to earphones, a speaker, or a smartwatch, within about ten metres) and Wi-Fi (a wireless LAN that lets devices connect to a network and the Internet within a home, office, or hotspot).