7.7.2 Advantages And Limitations
SDM represents the modern extension of multiplexing into the spatial domain. Whereas early communication systems relied on separating users in frequency or time, contemporary high-capacity networks exploit the vector nature of electromagnetic fields and the spatial structure of propagation channels. In effect, SDM recognizes that space itself is a multiplexing resource.
With spectrum increasingly scarce and demand for data continuing to grow, SDM—particularly in the form of multibeam satellites, massive MIMO, and multicore optical fibers—has become one of the most powerful tools for expanding communication system capacity.
SDM has the following advantages:
- Increased capacity without additional spectrum.
- Improved spectral efficiency.
- Enhanced interference management.
- Flexible user allocation.
Despite those advantages, SDM has a number of limitations:
- Requires multiple antennas or spatial channels.
- Increased signal processing complexity.
- Sensitive to propagation environment.
- Hardware size constraints (particularly at lower frequencies).
- Channel state information (CSI) is required for optimal performance.