what is the frame structure in LTE




There are two radio frame structures for LTE: frame structure type 1 (FS1) for full duplex and half duplex FDD, and frame structure type 2 (FS2) for TDD. The frame structure for full duplex FDD is shown in Figure .

FS1 is optimized to co-exist with 3.84 Mbps UMTS system. This structure consists of ten 1 ms sub-frames, each composed of two 0.5 ms slots, for total duration of 10 ms. The FSQ is the same in the uplink and downlink in terms of frame, sub-frame, and slot duration, although the allocation of the physical signals and channels is quite different. Uplink and downlink transmission are separated in the frequency domain.

One subframe The structure of FS2 is much more flexible than the structure of FS1. An example of an FS2 structure is shown in Figure 4. This example shows 5 ms switch-point periodicity and it consists of two 5 ms half-frames for a total duration of 10 ms. Sub-frames consist of either an uplink or downlink transmission or a special sub-frame containing the downlink and uplink pilot timeslots (DwPTS and UpPTS) separated by a transmission gap guard period (GP). The allocation of the sub-frames for the uplink, downlink, and special sub-frames is determined by one of seven different configurations. Sub-frames 0 and 5 are always downlink transmissions, and sub-frame 1 is always a special sub-frame, but the composition of the other sub-frames vary depending on the frame configuration.






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