NOMA vs OMA: Understanding the Difference in 5G Wireless

This page compares NOMA vs. OMA and mentions the difference between NOMA and OMA used in 5G Wireless technology.

NOMA stands for Non-Orthogonal Multiple Access, and OMA stands for conventional Orthogonal Multiple Access.

Introduction: Both NOMA and OMA are multiple access techniques that utilize the power/code domain and the time/frequency domain, respectively. TDMA and OFDMA are examples of OMA techniques.

NOMA | Non-Orthogonal Multiple Access

NOMA is a multiple access technique employed in 5G cellular wireless networks. The main function of NOMA is to serve multiple UEs (User Equipments) using a single 5G-NB (Node B or Base Station). It serves multiple users on the same time/frequency resources.

There are two main techniques employed in NOMA for multiple access:

• Power domain: NOMA achieves multiplexing based on different power levels.
• Code domain: NOMA achieves multiplexing based on different codes.

Transmit side: NOMA uses superposition coding at the transmitter end. Different power levels are assigned to users. As shown in Figure 1, the Base Station transmits superposed signals to User#1 and User#2. User#2 uses high gain, and User#1 uses low gain.

Receive side: NOMA uses the SIC (Successive Interference Cancellation) technique to retrieve data from both users. At the receiver, User#2 (Strong User) subtracts the signal of User#1 through SIC and then decodes its own signal. User#1 (Weak User) treats the signal of User#2 as noise and decodes its own signal directly.

OMA | Orthogonal Multiple Access

• In OMA, the frequency domain is shared among users. As shown, U1 part of the frequency spectrum is allocated to User#1, and U2 part is allocated to User#2.
• Refer to the advantages and disadvantages of NOMA over OMA.
• Examples: TDMA, OFDMA

The following table summarizes the difference between NOMA and OMA.