FDMA

Based on access method:

• Frequency Division Multiple Access (FDMA)

FDMA or Frequency Division Multiple Access is an access method that is used by radio systems to share the radio spectrum. The terminology “multiple access” implies the sharing of the resource amongst users, and the “frequency division” describes how the sharing is done: by allocating users with different carrier frequencies of the radio spectrum.

In FDMA the given Radio Frequency (RF) bandwidth is divided into smaller frequency bands called subdivisions. Each subdivision has its own carrier frequency. A control mechanism is used to ensure that two or more earth stations do not transmit in the same subdivision at the same time. Essentially, the control mechanism designates a receive station for each of the subdivisions.

Source: Wikipedia

Examples of radio technology that are utilizing FDMA are APCO-25, EDACS and Tetrapol

TDMA

• Time Division Multiple Access (TDMA)

• TDMA or Time Division Multiple Access is an access method that is used by radio systems to share the radio spectrum. The terminology, “multiple access,” implies the sharing of the resource amongst users while the “time division” describes how the sharing is done: by dividing and allocating users into different timeslots in a carrier frequency of the radio spectrum.
• The shared users transmit in rapid succession, one after the other, each using their own timeslot. This allows multiple users to share the same transmission medium (e.g. radio frequency) while using only the part of its bandwidth they require.
• TDMA is used in the Global System for Mobile Communications (GSM) and Personal Digital Cellular (PDC). It is also used extensively in satellite systems, local area networks, physical security systems, and combat-net radio systems.
• Examples of radio technology that are utilizing TDMA are TETRA, OpenSky and iDEN.

Note: There are some other access methods such as CDMA (Code Division Multiple Access), SDMA (Space Division Multiple Access) and CSMA (Carrier Sense Multiple Access). However, these access methods have not been used in two-way radio technology.

Category: LEARNING CENTRE

Tags: CDMA, CSMA, FDMA, SDMA, TDMA, two way radio