There is saving of bandwidth by using multicarrier modulation with orthogonal frequency division multiplexing. MIMO achieves spatial diversity and spatial multiplexing. Arrayed waveguide gratings are commonly used for multiplexing and demultiplexing in WDM. In addition to improvements in these multiplexing systems, improved modulation techniques are being used. The multiplexing of multiple digital signals is much simpler to the multiplexing of analog signals. This makes FETs suitable for switching analog signals between paths (multiplexing). They are also used in trunklines that transmit multiple signals using frequency division multiplexing (FDM). A variant technology, called wavelength-division multiplexing (WDM) is used in optical communications. This is an asynchronous mode time-domain multiplexing which is a form of time-division multiplexing. S-Video and composite video mix the signals together by means of electronic multiplexing. Frequency-division multiplexing (FDM) is inherently an analog technology. MIMO can be sub-divided into three main categories&colon; precoding, spatial multiplexing (SM), and diversity coding. It provides services such as connection-oriented communication, reliability, flow control, and multiplexing. This development improved capacity and call quality compared to the previous frequency-division multiplexing schemes. A procedure similar to a time multiplexing method is used.