Below is an example of transport characteristics of an interactive service through DCH
The below is an example of the transport characteristics of a Signaling Radio Bearer through DCH
These two DCHs are multiplexed into a CCTrCH with the following TFCS (transport format combination set).
For a given TTI, TFC (Transport format combination) is chosen and used.
Q1. Which layer will decide TFC ?
Q2. What factors impact its decision?
A1: MAC layer
A2: Many factors
1. given current channel condition; if noisy channel, only some of the TFCs can be used
2. data buffers in the RLC layer
3. priority of the data in RLC buffer
RLC buffer is not a stream of bits, but a group of [...]
Yes!
Transport format combination (TFC) selection frequency is equal to the length of the shortest configured TTI duration.
During a given TTI, the selected transport formation combination (TFC) must reamin the same.
It can be changed by the transmitter from one TTI to another.
Such a change involves alterations in physical layer parameters suchas the spreading factor etc.
Thus, the receiver should detect the transport format combination that is being used at a given moment.
This can [...]
So confusing with transport format, transport format set ?
The fact: Several transport channels can be multiplexed in a single physical channel.
So, transport format combination (TFC) defines the number of transport blocks that are transmitted from each of the multiplexed transport channels in a given TTI.
Example:
DCH1:
{10ms, turbo coding, static rate matching parameter =1}
{40 bits, 40 bits}
DCH2:
{10ms, [...]
