NDI stands for New Data Indicator.

• It values may be 0,1.
• If NDI value is not changing then it is case of retransmission.
• If NDI bit is changing from 0->1 then it is new data transmission.
• The changing of NDI value from 0->1 ,1->0 is called NDI toggling.

In LTE, NDI stands for “New Data Indicator.” It is a flag that is included in the Downlink Control Information (DCI) message to indicate whether the transmission or retransmission is carrying new data or a retransmission of previously transmitted data.

The NDI flag is used by the receiver to determine whether the received data is new or a retransmission of previously received data. If the NDI flag is set to 1, it indicates that the data being transmitted is new data that has not been previously received. If the NDI flag is set to 0, it indicates that the data being transmitted is a retransmission of previously received data.

The NDI flag is an important parameter for the Hybrid Automatic Repeat Request (HARQ) protocol, which is used in LTE to ensure reliable transmission of data over wireless networks. When the receiver detects errors in the received data, it sends a Negative Acknowledgement (NACK) message to the transmitter, indicating that the data needs to be retransmitted. If the NDI flag is set to 1, it means that the retransmission is carrying new data, and the transmitter needs to use a new redundancy version (RV) to encode the data. On the other hand, if the NDI flag is set to 0, it means that the retransmission is carrying previously transmitted data, and the transmitter needs to use the same RV as before.

Overall, the NDI flag plays a critical role in the reliable transmission of data over LTE networks by enabling efficient and effective use of the HARQ protocol.