# Baseband Technology (OFDMA) Day 5: July 23th, 2021 ###### tags: `PNJ` `5G O-RAN` `ITB NTUST 5G course` :::success ### 3 Most Important Aspects 1. Baseband Technology (OFDM & OFDMA) 2. OFDM System 3. Modulation and Demodulation ::: :::info ### Summary OFDM stands for Orthogonal Frequency Division Multiplexing. OFDM is a multiplexing technique that divides the available bandwidth into multiple orthogonal sub-carriers. Each sub-carrier can be modulated independently and carries different information. FDM stands for Frequency Division Multiplexing. This technique can be used to optimize frequency utilisation for communication. It can increase the bandwidth efficiency on a communication. OFDM also has advantage in term of fading. It is more resistant to fading due to the width of the bandwidth used and the multipath effect that occurs on the channel. OFDM uses many sub-carriers with narrow bandwidth (smaller than coherence bandwidth). In OFDM, Single data source attaches all the sub-channels. Applications of FDM are in radio and satellite communication. Applications of OFDM are in LTE technologies and broadband internet. The Characteristics OFDM there are: ![](https://i.imgur.com/GLwKcJI.png) In the OFDM system, the arrangement of several OFDM symbols forms a single OFDM Frame. In general, there are two types of frames, namely Uplink Frame OFDM and Downlink Frame OFDM. Uplink is a communication line from the Subscriber Station (SS) to the Base Station (BS). On the other hand, Downlink is a communication path from BS to SS. Modulation is the process of changing a periodic wave with a certain frequency in order to be able to carry information. Demodulation is the process of returning the bit value of the modulated signal y which consists of Real (I) and Imaginary (Q) components received. The modulation-demodulation process is also known as Mapper-Demapper, which is the mapping of binary samples to complex number samples and vice versa (bit symbol). ::: :::info ### Comment Orthogonal Frequency Division Multiplexing (OFDM) is an efficient modulation format used in modern wireless communication systems including 5G. OFDM combines the benefits of Quadrature Amplitude Modulation (QAM) and Frequency Division Multiplexing (FDM) to produce a high-data-rate communication system. :::