NOMA vs OMA: Understanding the Difference in 5G Wireless
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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.
Specifications | NOMA | OMA |
---|---|---|
Full Form | Non-Orthogonal Multiple Access | Orthogonal Multiple Access |
Receiver complexity | High | Low |
Energy consumption | More | Less |
Number of users/cluster | Lower | Higher |
Number of user pairs | Less | More |
System throughput (User fairness) | Larger | Smaller |