Interference Spectrum Estimation In LTE System

As one of the most important standards in the next generation wireless system,LTE system’s prospect and status in the future wireless communication industry havebeen widely recognized. There may be exist variety kinds of interference in the LTEservice area. These interferences may seriously degrade the system performance.Hence, interference detection is very important for the elimination of interference,wireless resource scheduling and network optimization in the LTE system.This dissertation focuses on the estimation the illegal signal spectrum exists inLTE service cells. Considering the modulation and coding scheme of PDCCH arefixed, and PDCCH signal appears regularly in time-frequency resource grid and onlytransmit diversity is used when the base-station has multiple antennas, aPDCCH-based interference spectrum estimation scheme was proposed.In case of base station use single antenna, estimation of PDCCH signal isobtained via brutal force search, then the estimation of interference signal is obtainedby removing PDCCH signal from the received signal. The main disadvantage oftraditional pilot-aided channel estimation algorithm is low accuracy of estimation,since the channel estimation error will propagate to interference signal spectrumestimation. Hence a channel estimation algorithm combines PDCCH demodulationand decoding is proposed, the accuracy of estimation is significantly improved withthe cost of the negligible calculation complexity increase.As most of the base stations in LTE system configured multiple antennas, aninterference spectrum estimation method for two transmit antenna is proposed and itcan be extended to four antennas case.The simulation results shown that the proposed algorithm can detect theinterference signal spectrum mixed the LTE signal with acceptable accuracy.