When synchronization channel transmission frame, each bit is transmitted continuously.
:( need to solve problems sending and receiving ends)
1. In the transmitter, there will be idle before the transmission data frame bits, these bits to the receiving side, the receiving end how to determine whether it is a data frame or idle bits.
2. When the sending end is completed, enabling the receiver to know the data frame has ended.
Approach: the use of special filling position bits idle bit pattern.
The receiving end first determines whether the data is transmitted over a special pattern, if not accepted, when the pattern is not found, showing Frame (frame) starts transmission;
Receiving the pattern is found, indicating the end of Frame.
Which in turn raises a problem: If the specific pattern appears in a transmission frame, is how to determine the frame data or frame end of transmission?
The need to solve the problem: to adopt the necessary measures to eliminate the pattern Frame may appear.
Way: '0' bit insertion-deletion methods.
Special pattern image above Use 01111110, by using the pattern of 6 consecutive characteristic 1.
Frame content pattern cancellation method - '0' bit insertion method
When the bit sequence of five consecutive 'is 1'bit, unconditionally inserting a' 0'bit. Thus, the frame definitely more than 5 '1'bit consecutive not be the case.
Frame Content Recovery Method - '0' bit deletion method
Upon receiving, when successive received 5 '1'bit, and the sixth bit is' 0 ', the unconditional delete' 0'bit; if the sixth bit is '1', the first 7bit is '0', He met the special pattern, the receiving end. If the first 7bit or '1', it indicates that a channel error (certainly wrong frame, the data frame transmitted and can not have a special pattern 7 consecutive '1'bit present)
