Wireless Communication

Simulation of BER of Non orthogonal multiple access (NOMA) in AWGN channel - MATLAB code with explanation You can download the MATLAB code directly here . In the previous two posts, we took a toy example to understand the concept of NOMA and to prove to ourselves that NOMA indeed works as expected. As we said before, NOMA uses superposition coding at the transmitter end and successive interference cancellation at the receiver end. In this post, we will see how to simulate a simple two user NOMA system using MATLAB. We will be plotting the BER performance of NOMA in an additive white gaussian noise (AWGN) channel. The AWGN assumption here is made to keep things simple so that we can pay more attention to the actual skeleton of NOMA implementation. We will improve on this model and do the similar exercise over a Rayleigh fading channel in the next post . The MATLAB code used in this example is available for download here . See this post on How to do power allocation i

NOMA uses power domain multiplexing of users sharing same time and frequency resources. This is accomplished by performing superposition coding at the transmitter and successive interference cancellation (SIC) at the receiver. In the previous post , we saw a graphical view of superposition coding. In this post, we will see how SIC is carried out to decode the superposition coded signal at the receiver side. As a quick recap, we had two users with data x 1 and x 2 respectively. ( What if we had more than two users? ) We first did BPSK modulation to both x 1 and x 2 . Then we obtained the superposition coded signal as x = √a 1 x 1 + √a 2 x 2 where, a 1 and a 2 are the power weights given to x 1 and x 2 respectively, such that, a 1 + a 2 = 1. We took an example of x 1 = 1010 and x 2 = 0110. After BPSK modulation and choosing a 1 = 0.75 and a 2 = 0.25, we obtained the superposition coded signal x, as shown below: Before decoding, let us take a look at SIC al

Non Orthogonal Multiple Access (NOMA) is a candidate multiple access scheme for 5G. The fact that NOMA allows multiple users to transmit and receive simultaneously using the same frequency may appear intriguing. The two key operations that make NOMA possible are superposition coding which must be done at the transmitter side and successive interference cancellation (also known as SIC) at the receiver side. In this post we will see about superposition coding. Let us say two users User 1 and User 2 are going to communicate simultaneously using the same frequency. Let x 1 denote User 1's data and x 2 denote User 2's data. For simplicity, let us assume that each user has just 4 bits of data to send. This assumption is far from reality, but is sufficient to understand the basic working of NOMA. Let x 1 = 1010 and x 2 = 0110. A graphical view of x 1 and x 2 is shown below. x 1 and x 2 must undergo digital modulation before transmission. Let's use BPSK fo