TDD vs. TDMA: Understanding the Difference

This page describes the difference between TDD and TDMA.

TDD

TDD stands for Time Division Duplex. It’s a communication method where two wireless devices communicate on the same frequency but at different times.

For example, WiMAX uses a TDD frame, which is divided into a downlink subframe and an uplink subframe. Downlink communication goes from the Base Station (BS) to Subscriber Stations (SSs), and uplink communication goes from the SSs to the BS. This arrangement forms the TDD frame in the air.

An alternative method is FDD (Frequency Division Duplex), which uses two different frequencies for simultaneous communication, one for transmitting and one for receiving.

Image alt: TDD vs TDMA

Refer to this article for TDD Application used in LTE system and a comparison between TDD and FDD.

TDMA

TDMA stands for Time Division Multiple Access.

It’s a technique used to share common resources, like frequencies or PN codes, among multiple users.

For instance, in GSM, a frequency is shared among multiple Mobile Stations using TDMA.

Other multiple access techniques include FDMA and CDMA.

Refer to TDMA basics and types and TDMA comparison with FDMA and CDMA for more information.

To understand the in-depth differences between these terms, refer to the following resources:

• What is the Difference between FDM and OFDM?
• Difference between SC-FDMA and OFDM
• Difference between SISO and MIMO
• Difference between TDD and FDD
• Difference between 802.11 standards viz.11-a, 11-b, 11-g and 11-n
• OFDM vs OFDMA
• CDMA vs GSM