Received Signal Strength Indication is a measurement used across various types of wireless communication technologies, including but not limited to LTE, Wi-Fi, and other RF communication systems. It quantifies the overall power observed by the receiver from a signal in its current environment, regardless of the specific type or source of that signal.
RSSI is generally expressed in dBm and typically ranges from -30 dBm (a very strong signal) to -100 dBm (a weak signal), though these values can vary depending on the specific technology and the conditions of the environment. Unlike RSRP, which specifically measures the power of cell-specific reference signals in an LTE network, RSSI measures the total power received from all sources, including co-channel signals, adjacent channel interference, and background noise.
RSSI is a basic measure of channel power, including both the wanted signal, and unwanted signal components such as noise. RSSI is measured in dBm. A high RSSI is desirable as it logically follows that the maximisation of RSSI should result in maximisation of the wanted signal, the two generally have a positive correlation. However, maximisation of RSSI may result through receiving strong unwanted signals, such as sources of interference.