O-RAN and Massive MIMO Cell-free Exploration
"By disaggregating the functionalities in multiple virtual units at the KU Leuven Distributed Massive MIMO testbed, we will benefit from the flexibility of the O-RAN architecture and the capacity increase of the cell-free massive MIMO system."
Prof. Sofie Pollin, Networked Systems Group, KU Leuven
The Challenge:
The integration of cell-free and O-RAN is starting to get attention, but so far, there is a lack of experimental results.
The Solution:
Using NI equipment, KU Leuven created a Massive MIMO testbed that allows the distribution of the antenna elements by applying different precoding matrices to selections of the antennas.
O-RAN Vision
The vision of O-RAN is the disaggregation of the RAN into different functional nodes, such as centralized unit (O-CU), distributed unit (O-DU), and radio unit (O-RU). These nodes will be provided by multiple vendors and their functionalities will be integrated seamlessly and securely.
In parallel, scalable cell-free massive MIMO architectures are expected to improve the transmission rate using distributed, cooperative signal-processing techniques. The integration of cell-free and O-RAN is starting to get attention, but so far, there is a lack of experimental results.
NI and KU Leuven Massive MIMO Testbed
The flexible NI KU Leuven Massive MIMO testbed allows the distribution of the antenna elements. It can emulate virtual DUs (vDU) and virtual RU (vRU) by applying different precoding matrices to selections of the antennas. In addition, the testbed's 64-patch antennas can be deployed and distributed into multiple arrays, to emulate small cell-free scenarios.
During the first attempt to virtually integrate O-RAN and cell-free systems, we consider the study case of splitting the decoder across a single vDU or two vRUs, where the vRU coherently combines the signal of eight antennas.
The flexible NI KU Leuven Massive MIMO testbed allows the distribution of the antenna elements. It can emulate virtual DUs (vDU) and virtual RU (vRU) by applying different precoding matrices to selections of the antennas. In addition, the testbed's 64-patch antennas can be deployed and distributed into multiple arrays, to emulate small cell-free scenarios.
During the first attempt to virtually integrate O-RAN and cell-free systems, we consider the study case of splitting the decoder across a single vDU or two vRUs, where the vRU coherently combines the signal of eight antennas.
In Figure 2, you can see that the DU has a larger gain and hence larger signal amplitude.
These initial results show that real-time experiments to validate several O-RAN splits and control API is possible. The next step is to build the relevant building blocks for scaling up O-RAN cell-free experiments with more RU, higher frequencies and bandwidths. This will be the work done in the Horizon Europe project 6G-BRICKS.
