What technique is used for transmitting two or more streams of data in the same frequency channel?

The technique used for transmitting two or more streams of data in the same frequency channel is spatial multiplexing. This approach takes advantage of multiple antennas at both the transmitter and receiver to create separate data streams that can be transmitted simultaneously over the same frequency spectrum. The unique spatial pathways created by the multiple antennas allow for the differentiation between the data streams, enabling increased capacity and efficiency in transmission.

Spatial multiplexing is particularly effective in wireless communications, where it enhances bandwidth utilization without requiring additional frequency spectrum. By utilizing techniques such as multiple-input multiple-output (MIMO) technology, spatial multiplexing significantly improves throughput and reliability in wireless networks.

Time division multiplexing, frequency division multiplexing, and waveform multiplexing are also methods of combining multiple signals for transmission, but they operate differently. Time division multiplexing allocates different time slots for each data stream, while frequency division multiplexing assigns different frequency bands to each stream. Waveform multiplexing involves using different signal shapes to distinguish between data streams. However, none of these techniques utilize spatial separation to achieve simultaneous transmission in the same frequency channel like spatial multiplexing does.