What is spatial multiplexing

SDM - Space Division Multiplex (space division multiplex)

The space division multiplex process involves the transmission or switching of several signals or connections via several available transmission paths. A transmission path is made exclusively available to a signal. A distinction can be made between wired and wireless room multiplex.

Wired space division multiplex

The wired room multiplex method is used in analog and digital switching technology. The core is the cross bar switching, which is also referred to as a switching matrix. It is a crosspoint matrix that is arranged two-dimensionally in rows and columns. The crosspoints are located in the crossing points, each of which can connect a row with a column. In the matrix, a connection can be established or canceled using control commands for switching the crosspoints on and off. The connection is usually switched through with multiple cores (speech cores and control cores).
As required in switching technology, this results in absolute accessibility of all participants, where everyone can be connected to everyone. However, this method is paid for with a large space requirement. So this works more with a small number of participants.

Wireless space division multiplex

The wireless room multiplex method is always used in radio technology when a frequency is to be used several times. The same frequency is used with a sufficiently large spatial distance in two different locations. The distance must be so great that the radio signals of the different transmissions cannot interfere with one another.

The wireless room multiplex method is also used for frequency allocation. For example in broadcasting, cellular mobile communications, WLANs and in radio relay networks. There, the allocated frequencies are assigned multiple times and used at different locations. This is possible because the transmission power is limited to a certain frequency and the range of the signal is therefore limited. This enables you to use the same frequency multiple times, provided the signals do not overlap.

MIMO - Multiple Input Multiple Output

Another form of wireless room multiplex is used with multiple input multiple output (MIMO) in WLAN and mobile communications. MIMO is the generic term for processes that improve radio connections with several antennas used in parallel.

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