Note that RB vs. SRB

At the UTRAN side, RLC and above protocols are located at RNC.

MAC protocols: some functionalities are at Node B, others are at RNC.

Then, first you need to be familiar with the terminologies in the below picture.

Transport format combination (TFC)  selection frequency is equal to the length of the shortest configured TTI duration.

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 be done explicitly by means of TFCI (indicator), included in the control physical channels, or by means of blind detection procedures.

This is equivalent to transport format set for transport format when several transport channels are multiplexed.

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, convolutional coding, static rate matching parameter =3}

{320 bits, 320 bits}

—————-

a set of allowed transport formats for a given transport channel.

As a result, it limits the max number of transport blocks that can be transmitted in a TTI, or it limits the max instantaneous bit rate.

Example:

{10ms, turbo coding, static rate matching parameter =1}

{40 bits, 40 bits}; {40 bits, 80 bits}; {40 bits, 120 bits}

It consists two parts:

1. semistatic

TTI, error protection scheme, size of CRC, static rate matching parameter,

2. dynamic

transport block size, transport block set size

Example:

{10ms, turbo coding, static rate matching parameter =1}

{320 bits, 640 bits}

——————————————————–

Interesting point:

The number of transport block set size defines the the instantaneous bit rate or equivalently the spreading factor that should be used in the physical layer.

If you know the answer, I’ll appreciate if you let me know.

A set of simultaneous transport blocks is the transport block set.

The transmission time interval (TTI) is the duration of each transport block set.

This can be 10, 20, 40, 80 ms.

TTI does not tell you data size. It tells you how often the transport channel data rate can be changed.