Here I write Interference Margin in simple word and basic definition of interference margin in LTE. Let understands it.

Interference margin accounts for the increase in the terminal noise level caused by the interference from other users.

LTE uplink is orthogonal if it is within the same cell so there is no intra-cell interference. However, we still need a margin for the other cell interference. The interference margin in practice depends heavily on the planned capacity so there is a tradeoff between capacity and coverage just like other cellular technologies.

The interference margin indicates the degradation of system receive performance caused by internal interference in the system due to system traffic. In fact, due to the frequency division nature of LTE, there is also a close correlation between actual traffic load and interference margin experienced by the network.

Nonetheless, the orthogonal nature of LTE allows a smaller provisioning of cell breathing and interference margin when compared with WCDMA/HSUPA/ EVDO. Various techniques (e.g. Femto Cell, Relay, Coordinated Multi-Point) are being proposed by the industry to reduce the level of interference over thermal increase which will further improves the capacity and throughput offered by LTE in the future.