Hello All,

The concept of TTI in #LTE has always confused me. I am giving a brief understanding from a base station perspective.

So, assuming BW is fixed (e.g. 20 MHz), the max. overall throughput is also fixed. I say max. because user data throughput can change based on the modulation order etc.

So, now, another variable, that is, sub-frame type is introduced, which decides DL (Downlink) vs UL (Uplink) data.

with this understanding of mine, I would like to get some clarity on the TTI:

1) TTI decides how often data is sent by upper layer to L1 layer but does it mean that upper layer is mandated to send it always or this is more of max. condition

2) due to sub-frame type, where DL data can reduce and UL data can increase, how would the TTI data fit if the allowed DL data rate changes as per the sub-frame selected