E1 framing and unframed structure

First of all, it needs to be explained that E1 adopts the European standard, and each E1 is divided into 32 time slots, which are 0~31 time slots, each time slot is 64k, that is 32*64k=2048k, which is equal to 2M, because some people in the industry also call E1 "2M". In practical applications, E1 is further divided into framing and unframing formats.

In layman's terms, the framing format is to encapsulate the data carried by E1 into a single "small packet" for sequential transmission. The framing format is further divided into 30 and 31 formats. The 30 format means that E1's 0 time slot and 16 time slot are used for other purposes, and 1~15 time slots and 17~31 time slots are used to carry valid user data; The 31 formats 0 time slots are used for other purposes, and 1~31 time slots are all available to carry valid user data.

According to popular understanding, the unframed format does not play a "packet", and 0 to 31 time slots of E1 are transmitted in an unordered manner, and these 32 time slots can be used to carry valid service data.

The biggest difference between framing and non-framing is the use aspect of the 0 and 16 time slots. In practical applications, the framing format is more used on PCM devices, and the unframed format is more used for E1 to Ethernet co-transfer. Because both 0 and 16 time slots can transmit data, Ethernet bandwidth It can be maximized, otherwise transmitting Ethernet in framing format is equivalent to reducing the bandwidth of 2 slots.