I understand, IM-NOMA can get quite technical. Let's break it down without diving deep into the math (referring to the mentioned paper by Bae et al. for specifics).

Here's how IM-NOMA works (conceptually):

Imagine a system with a base station trying to communicate with two user equipments (UEs) simultaneously. Traditional NOMA relies on power control to differentiate between strong and weak users. IM-NOMA adds another layer of complexity.

Benefits of IM-NOMA:

• Improved spectral efficiency: Utilizes subcarrier activation for user identification, reducing overhead.
• Increased system capacity: Allows serving multiple users simultaneously.

2-User Received Signal Formula (Simplified):

The actual formula in the paper will involve complex number representations and summation. Here's a simplified view for understanding:

Let x1(t) and x2(t) be the data signals of User 1 and User 2, respectively.

h1 and h2 represent the channel coefficients between the base station and User 1 & User 2.

Base Station Signal (s(t)):

s(t) = a1 * f1(t) * x1(t) + a2 * f2(t) * x2(t)

where:

• a1 and a2 are scaling factors for power control (as in traditional NOMA).
• f1(t) and f2(t) are functions representing the subcarrier activation patterns based on the assigned indices to each user.

This simplified formula shows how the base station combines user data with their corresponding subcarrier activation patterns (determined by the indices).