Bit-staffing

It is obvious, that by transfering frame over communication channel its contents between two flags (opening and closing) should not have fragments of a kind 01111110; otherwise it will be identified by the receiver as the frame end. Therefore, for the purpose of creation of the "transparent" channel, contents of the composited frame before sending in the channel are exposed to special processing. If in the sequence meets five ones successively, after them it is inserted 0. On reception, before frame decoding return operation is made: if after five successively following ones is 0, it is excluded. This method is called bit stuffing. For example, we will consider a fragment of a contained frame between flags:

After frame formatting in the transmitter

...010111110001111110...

After processing in the transmitter

...01011111 00011111 10...

In the receiver (before frame decoding)

...01011111 00011111 10...

Date: 2015-02-16; view: 1248