| Summary: | 碩士 === 國立臺北科技大學 === 電機工程系所 === 102 === In recent years, the research on cooperative communications has received much attention. By using relay stations (RSs) the transmission efficiency of downlink 4G communication system can be significantly improved. Furthermore, with the help of cognitive radio (CR), the unauthorized user can borrow the bandwidth of authorized user, thus increasing the bandwidth usage efficiency, and alleviating the problem of traffic congestion. This thesis aims to estimate the signal-to-noise ratio (SNR) over the orthogonal frequency division multiple access (OFDMA) system, where additive white Gaussian noise (AWGN) channel and path loss are considered. The estimated SNR together with rely station and cooperative communications are then used for channel assignment in order to improve bandwidth usage efficiency. Finally, the transmission capacity evaluated based on the estimated SNR and real SNR are compared. The result shows that the overall error between them is only 3.5%, indicating the potential of the estimation scheme for transmission capacity prediction.
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