Physical Layer Initial Learning

1. Physical layer to solve those problems? What are the main features of the physical layer?

   The physical layer needs to consider how to transmit the data bitstream on the transmission media connected to various computers, rather than the specific transmission medium.

   The physical layer has the following characteristics:

   1) Mechanical Properties

   2) Electrical characteristics

   3) Functional characteristics

   4) Process characteristics

2. Data communication System Model classification and the role of major components

Data communication system model can be divided into three categories: source system, transmission system, target system

The source system generally includes: source point, transmitter

The purpose system generally includes: end point, receiver

The transmission system between the source and destination systems may be a simple transmission line, or it may be a complex network system connected to the source system and the destination system

3. Shannon Formula

Shannon formula:c=b*log? (1+s/n) (bit/s)

Signal-to-noise ratio: signal-to-noise ratio (DB) =10*log10 (S/n)

b is the limit value of the code element rate (indicated by the Nyquist b=2h,h as the channel bandwidth, Unit baud), S is the signal power (watts), N is the noise power (watts).

the S/N in the Shannon formula is the ratio of the power of the signal to the noise, as dimensionless units. such as: s/n=1000 (i.e., the signal power is 1000 times times the Noise power)

Physical Layer Initial Learning