Uplink MU-MIMO: Eliminating Synchronization Requirements

In wireless LANs (WLANs), network-wide time and frequency synchronization among user devices is widely regarded as a necessity for uplink MU-MIMO. Therefore, to enable uplink MU-MIMO in 802.11ax, dedicated MAC protocols (e.g., trigger frame and timing advance mechanism) have been employed to synchronize user devices in the time and frequency domains. Such MAC protocols increase not only network complexity but also communication overhead.

In this demo, we show that the time and frequency synchronization among user devices is not a necessity for uplink MU-MIMO in WLANs. We developed a practical uplink MU-MIMO solution which does not require timing and clock frequency alignments among user devices. The key component in our solution is a new PHY design for AP’s receiver, which can decode the concurrent signals from multiple asynchronous user devices. Experimental results show that uplink MU-MIMO is feasible in asynchronous wireless networks.

Downlink MU-MIMO: Minimizing Communication Overhead