What does SI- Window means in LTE?

Question

It is my understanding that more SIBs can be scheduled inside a single SI message, but it is not clear to me how to read them inside an SI message, once I know where to find it. Are their contents simply one after another (as in let's say [SIB2 content | SIB3 content]) or is there a special structure to them?

Answer 1

In order to make sure the SIBs are received by the UE, an SI-window is defined to enable multiple transmissions of the SI message within the window. The length of the SI-window can be set to 1, 2, 5 10, 15, 20 or 40 ms. Within an SI-window, only one SI message can be sent, and may be repeated multiple times. When a UE tries to acquire an SI message, it listens from the starting of the SI-window until the SI message is received.

The following figure shows an example of the configuration of the periodicities of SIBs 2, 3, 6, and 7. Here, we use two SI messages, SI1 and SI2. SI1 contains SIB2 and SIB3 with a periodicity of 16 radio frames, while SI2 contains SIB6 and SIB7 with a periodicity of 64 radio frames. Assume that the SI-window length is 10 ms (1 radio frame).