MU-MIMO vs OFDMA | difference between MU-MIMO and OFDMA
This page compares MU-MIMO vs OFDMA and mentions difference between MU-MIMO and OFDMA. MU-MIMO stands for Multi-User Multiple Input Multiple Output and OFDMA stands for Orthogonal Frequency Division Multiple Access.
MU-MIMO
• In MU-MIMO, multiple streams are transmitted at the same time as shown in figure-1. Individual users are
targetted via beamforming technique. Hence overall capacity is increased.
• Advantages: It increases capacity, MU-MIMO results in higher speeds per user.
It is ideal for high bandwidth applications.
• Application: Used in both uplink and downlink of 802.11ax, in downlink of 802.11ac
OFDMA
• It allocates subcarriers to users based on their needs.
Hence OFDMA does not increase capacity but it uses more effectively.
• In OFDM, all the subcarriers of a symbol are allocated dedicately to individual user all the time.
Hence resources are wasted if there is no data to be transmitted during that time interval.
• In OFDMA, multiple users can be multiplexed at the same time, each having its on dedicated set of subcarriers.
Hence multiple users with varying bandwidth can be scheduled simultaneously. The figure-2 depicts OFDM and OFDMA frame structures.
As shown all the subcarriers are allocated at a time to one user dedicately in OFDM.
In OFDMA, RU (Resource Unit) made of subchannel and number of symbols are allocated to individual
users as shown.
• Advantages: It increases efficiency. It reduces latency. It is ideal for low bandwidth applications.
• Application: Used in cellular wireless technologies such as WiMAX (16e), LTE and 5G.
It is also used in 802.11ax.
Conclusion: Both MU-MIMO and OFDMA techniques complement each other.
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