NOMA vs OFDMA | difference between NOMA and OFDMA | 5G

This page compares NOMA vs OFDMA and mentions difference between NOMA and OFDMA used in 5G Wireless technology. NOMA stands for Non-Orthogonal Multiple Access and OFDMA stands for Orthogonal Frequency Division Multiple Access.

Both NOMA and OFDMA are multiple access techniques. NOMA utilizes power domain or code domain where as OFDMA utlizes frequency/time resources to serve multiple users (i.e. UEs) in a cell by 5G-NB.

NOMA | Non-Orthogonal Multiple Access

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

There are two main techniques employed in NOMA for multiple access.
• Power domain: Here NOMA achieves multiplexing based on different power levels.
• Code domain: Here NOMA achieves multiplexing based on different codes.

NOMA, Non-Orthogonal Multiple Access

Transmit side: NOMA uses superposition coding at the transmitter end. The different power levels have been assigned to users. As shown in the figure-1, Base Station transmits superposed signals to User#1 and User#2. Here User#2 uses high gain and User#1 uses low gain as shown.

Receive side: NOMA uses SIC (Successive interference cancellation) technique to retrieve data of both the users. At receiver, User#2 (Strong User) substracts signal of user#1 through SIC and later decodes its own signal. User#1 (Weak User) treats signal of User#2 as noise and decodes its own signal directly.

OFDMA | Orthogonal Frequency Division Multiple Access


• In OFDMA technique BS (Base Station) shares its resources by transmitting to UEs at different time instants and frequencies.
• OFDMA allocates subchannels and time slots to the users based on desired bandwidth or data rate. Each of the subchannels are mapped with few number of subcarriers after permutations and hence OFDMA is robust against fading.
• The technologies such as Mobile WiMAX, LTE, LTE-advanced and 5G uses OFDMA technique for resource sharing.
Refer OFDM Vs OFDMA >> and SC-FDMA Vs OFDMA >> for more information on OFDMA technique.

Following table summarizes difference between NOMA and OFDMA.

Specifications NOMA OFDMA
Full form Non-Orthogonal Multiple Access Orthogonal Frequency Division Multiple Access
Spectrum Efficiency Higher Lower
Capacity (Number of users/cell) Less More

Also refer difference between NOMA and OMA >> for more information.


This 5G tutorial also covers following sub topics on the 5G technology:
5G tutorial
Difference between 4G and 5G
5G testing and test equipments
5G network architecture

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