How is Basic Frame Structure in LTE ?
- In FDD, the DL and UL Radio Frames (RFs) are not on the same carrier.
- The RF frame is called Type 1 by the 3GPP.
- The RF length is 10 ms.
- The radio frame is made up of 10 sub-frames of 1 ms.
- Each sub-frame is made up of 2 slots of 0.5ms.
A Frame structure type 2 is also defined and is applicable to TDD
- 7 symbols in case of normal CP (guard time between symbols)
Tcp = Cyclic Prefix duration
Tecp = Extended Cyclic Prefix duration
- The frame structure for the type 2 frames used on LTE TDD is somewhat different.
- The 10 ms frame comprises two half frames, each 5 ms long.
- The LTE half-frames are further split into five sub frames, each 1ms long.
The subframes may be divided into standard subframes of special subframes.
The special subframes consist of three fields:
- DwPTS – Downlink Pilot Time Slot
- GP – Guard Period
- UpPTS – Uplink Pilot Time Stot.
These three fields are also used within TD-SCDMA and they have been carried over into LTE TDD (TD-LTE) and thereby help the upgrade path. The fields are individually configurable in terms of length, although the total length of all three together must be 1ms.
Basic Frame Structure in LTE
The LTE frame lasts 10 milliseconds. It is divided into 10 subframes, with each subframe being 1 millisecond long. Within these subframes, there are slots, and each slot carries symbols. The number of symbols in each slot depends on the bandwidth and cyclic prefix length. If you are familiar with network frames, think of the LTE frame as the basic unit for transmitting data and control information.
Each subframe has its specific role. Some subframes are used to carry data, while others are dedicated to control information or synchronization. The frame structure allows LTE to handle large amounts of data efficiently. For example, when you are using a mobile device, the system ensures resources are allocated properly, allowing you to experience fast and reliable communication, even in a congested network.
Additionally, the frame structure includes synchronization and broadcast channels that make sure your device stays aligned with the network. This ensures that the LTE network can adapt to changing conditions, maintaining a stable connection for you as the user.