Spectrum efficiency measures how effectively a given frequency spectrum is utilized to transmit data. It quantifies the amount of data (in bits per second) that can be transmitted over a specific bandwidth (in hertz), typically expressed in bits per second per hertz (bps/Hz)
. More specifically, spectrum efficiency is calculated as the net bit rate (useful data rate excluding error-correcting codes) or maximum throughput divided by the bandwidth of the communication channel. This indicates how efficiently the limited frequency spectrum is used by a communication system's physical layer and sometimes by the medium access control layer
. Improving spectrum efficiency means increasing the amount of data transmitted over the same bandwidth, which is crucial because radio frequency spectrum is a limited and valuable resource. Enhancements can be achieved through advanced modulation schemes (e.g., quadrature amplitude modulation), multiple access techniques (e.g., TDMA, FDMA, CDMA), multiple input multiple output (MIMO) antenna systems, and dynamic spectrum management such as cognitive radio
. In wireless networks, system or area spectral efficiency also considers how many users or services can be simultaneously supported within a geographic area using a limited spectrum, factoring in radio resource management and interference mitigation techniques
. In summary, spectrum efficiency measures the data transmission capacity per unit of frequency bandwidth, and improving it allows more data to be sent over the same spectrum, enhancing overall network performance and capacity
