What is Synchronous mode of data transmission?

Question

RLC is one of the L2 layer in LTE radio protocol stack. It does many functions such as segmentation, re-assembling and along with that it supports various transmissions mode like transparent mode, acknowledgement mode and un-acknowledgement mode.
Now I want to understand for which type of RLC SDUs and PDUs transparent mode transmission is used.
Does the RLC create single RLC entity at cell level or at the UE level or at the bearer level ?

Answer 1

Asynchronous mode is also known as start-stop mode. This mode is used when data to be transmitted is generated at random intervals. For example, when a user communicates with a computer using a keyboard, the time interval between two successive keystrokes is random. This means that the signal on the transmission line will be in idle state for a long time interval between characters. With this type of communication, the receiver must be able to resynchronize at the start of each new character received. To accomplish this, each transmitted character or byte is encapsulated between an additional start bit and one or more stop bits. This mode is mainly used for the transmission of characters between a keyboard and a computer. Asynchronous transmission can also be used for the transmission of a block of characters or bytes between two computers. The time interval between successive characters is a variable entity

Answer 2

As I know, synchronous transmission is when the data traffic using the same path for uplink and downlink while Asynchronous is when the path is not same.