OFDM Signals and Their Spectrum Characteristics

OFDM signals represent a widely adopted modulation technique that divides high-speed data streams into multiple low-speed sub-signals for transmission. This approach enhances transmission efficiency and improves interference resistance. The spectral characteristic of OFDM signals features multiple subcarriers, each exhibiting a rectangular-function-like spectral shape. A critical implementation aspect involves guard interval insertion to mitigate inter-subcarrier interference. The guard interval functions by introducing time gaps between subcarriers, effectively reducing multipath interference impacts. This technique significantly improves signal transmission quality and reliability. From a coding perspective, guard interval implementation typically involves cyclic prefix insertion where the last portion of each OFDM symbol is copied to the beginning. This can be achieved using array manipulation functions like numpy.roll() in Python or circshift() in MATLAB. The guard interval length is usually calculated based on channel delay spread characteristics to ensure proper interference mitigation.