transmission time interval (UMTS) (TTI)

The Transmission Time Interval (TTI) defines the time interval of a Transport Block Set (TBS) in UMTS or in other digital mobile networks. It is concerned with the encapsulation ofdata from higher layers for transmission over radio links.

The TTI interval refers to the transmission duration on the radio link. For this radio transmission, the MAC layer generates a new Transport Block Set every 10 ms or a multiple thereof (20 ms, 40 ms, 80 ms). The Transmission Time Interval corresponds to the duration of a Transport Block Set and can be 10, 20, 40 or 80 ms. The TTI interval does not say anything about the file size.

In High Speed Downlink Packet Access( HSDPA), the TTI interval is reduced to 2 ms, which results in faster data transmission. In Evolution Data Optimized( EVDO), the frame size, which has a similar function to the transmission time interval, is 1.67 ms, and in EVDV it has variable lengths of 1.25 ms, 2.5 ms, 5 ms and 10 ms.