Spectrum Sensing of OFDMA Systems for Cognitive Radios
Date Issued
2007
Date
2007
Author(s)
Tu, Sheng-Yuan
DOI
en-US
Abstract
In order to fully exploit wireless radio resource and then increase spectrum efficiency, cognitive radios for future wireless communication systems shall sense wireless environments and identify interference so that the secondary system(s) may coexist with primary communication systems. As a result, sensing and cognition play a major functionality in cognitive radios. In this thesis, we acquire an effective set of cognitive information under a proposed spectrum sensing cycle for orthogonal frequency division multiple access (OFDMA) systems because of their potential and challenges. To avoid interfering with primary systems, detecting existence and activity of the primary system by measuring RSSI, tracking fundamental symbol rate of the primary system and is the first step in coexistence. Furthermore, using cyclic property of OFDMA signal and control and management signal in wireless communication systems, we can precisely determine existence and activity of the target OFDMA system in one frequency band, via Neyman-Pearson criterion. Simulation results show that near perfection detection is achieved even at low SNR. With a priori knowledge of frame structure in potential primary systems, communication parameters, such as data transmission rate and resource allocation state, can be extracted by decoding frame header. Finally, we can determine available radio resource with respect to cognitive radios using rate-distance relationship, while guarantee interference to primary systems. Moreover, by parametric adjustment, our sensing procedure can be applied to any state-of-the-art OFDMA systems nowadays.
Subjects
感知無線電
無線電資源
頻譜使用率
頻譜偵測
偵測/感知週期
正交多工分頻存取系統
速率距離關係
Cognitive radio
radio resource
spectrum efficiency
spectrum sensing
sensing/cognition cycle
orthogonal frequency division multiple access (OFDMA)
rate-distance relationship
Type
thesis
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