The physical layer is important for sending bits from one device to the other device. The physical layer is not concerned with the bits description, but it handles with physical relation to the mechanism with connection and signals acceptance.
The design issues of physical layers are as follows −
Whenever there is a requirement for data transmission by a device to another device, the request travels from the application layer to the data link layer. Thus the data link layer moves it to the physical layer, and the physical layer activates a physical link for the communication of bits.
The data link layer fist over the physical service data unit (PSDU) with one bit is the serial communication and "n" bits in parallel communication. It can support transparency of information, i.e., the bit sequences can be shared on a transmission medium through it without diminishing them.
Though the physical layer does not have some error control structure or flow control structure, it attempts to deliver the data bits in the similar series in which they were received from the data link layer.
Due to the lack of error and flow controls, it can appear that some data bits are duplicated, modified, or lost.
The physical layer is answerable for fault detections in the physical link. If it can recognize any fault in the physical connection, it can update the data link layer.
When the data sent is over, or the user requires a disconnection, the physical layer disconnects the connection by deactivating the physical link at the user’s request.
The physical layer provides the encoding of signals if required. It can also support bit synchronization for the communication of bits in both synchronous and asynchronous transmission.
The physical layer does not acquire character synchronization and frame synchronization. It is the responsibility of the data link layer.
A physical link can use an intermediate relay to reduce the issues like degradation of signal by noise, attenuation, etc., because of the interconnecting channel characteristics.
For this signal changing units are utilized in an intermediate relay where the computer signals are recreated, amplified, modulated, or equalized of media characteristics according to requirement. The physical layer gives out the activation and deactivation of the relay.