Physical and Logical Channels

Physical and Logical Channels

This diagram shows the difference between physical and logical channels. In this example, a physical channel transports information between two points using electrical signals. The physical channel is divided into frames that contain various fields (groups of information within the frame). This diagram shows that the frames on the physical channel are divided into 4 logical channels; 3 logical channels for data and one logical channel for control. The exact relationship between the frame structure and the logical channels is called mapping. This example shows two different mapping examples. In the first example, the bits in the information portion of each frame are equally divided. In the second mapping example, more bits are proportioned to channel 2. This results in a lower data transfer rate for channels 1 and 3 while channel 2 has a higher data transfer rate.