# IVC 5G O-RAN Summary

###### tags: `UNILA`

## 23th of July 2021

Name : Fajri Aditiya Putra
Team : B-5 5G O-RAN
Summary Day 4

**Basic Principles of OFDM & OFDMA**

* 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.


* Multi-carrier method, which is to divide the wide bandwidth into a narrow spectrum (sub-carrier) and overlap each other.
* The sub-carriers are orthogonal to each other, so there is no interference.
* Orthogonality between sub-carriers obtained by IFFT process


* ue to the width of the bandwidth used and the muti- path effect that occurs on the channel, the signal will experience a frequency selective fading effect.
* OFDM uses many sub-carriers with narrow bandwidth (smaller than coherence bandwidth), then each sub-carrier will only experience at fading,
* This reduces the complexity of the equalization process required on the receiver to compensate for the flat fading.

* Adaptive Modulation. OFDM systems can use various modulation types such as QPSK, 16-QAM and 64-QAM.
* Adaptive Coding. OFDM system can use various types of coding, both convolution coding and block coding, such as Viterbi, Turbo Deco-ding, RSA, BCH and so on.
* MIMO. OFDM systems also use a variety of MIMO methods to improve communication quality and capacity, such as spatial multiplex MIMO, and time multiplex MIMO.
* Duplex Mode. Ordinary OFDM systems can be applied to both TDD and FDD systems.