臺灣大學: 電信工程學研究所謝宏昀許哲豪Shu, Che-HaoChe-HaoShu2013-03-272018-07-052013-03-272018-07-052011http://ntur.lib.ntu.edu.tw//handle/246246/252872在次世代無線網路環境下，使用者需要更高的傳輸速率來滿足各式各樣的應用，因此ITU-R 在第四代通訊系統中定義了最高1Gbps 的傳輸速率。為滿足此需求，大部分的標準都使用多載波模式以提昇傳輸速度。但在多載波模式下，為了支援行動裝置的使用者，掃描換手對象的時間將被大大的延長，進而造成連線品質的下降。為了解決這個問題，本論文提出兩種掃描方式，Prioritized 以及Expedited掃描方式，並藉由載波間的交互關係來預測載波的訊號品質，進而減少掃描時間。在Prioritized 掃描方式中，我們藉由鄰近使用者回報的掃描報告，基地台便能預測載波的訊號品質並對使用者提出一掃描的優先順序。而在Expedited 掃描方式中，由於載波間的遮蔽效應有著高度的相關性，因此我們能藉由一載波的訊號來預測另一載波的訊號品質，進而減少掃描的誤差。從模擬結果中，我們發現透過此兩種方法，在不同網路環境下都能有效的降低掃描時間。Multi-carrier operation has been lately adopted by next-generation communication systems, such as IEEE 802.16m, as a promising technology to improve the system performance. However, a new issue arises when mobile stations need to scan the neighboring cells operating with multiple carrier. The handover decision might be delayed when the scanning time increases dramatically by the large amount of candidate carriers. A delayed handover decision would interrupt existing connections and incur serious damage to the system performance, such as throughput. To address this problem, this thesis focuses on how to reduce the scanning time while still maintaining a good handover quality. We reduce the scanning time from two aspects: the first one gives priority to the carriers of the neighboring cells, and the other reduces the unnecessary time if more effort may not increase the scanning performance. Based on the two concepts, the algorithm for prioritized scanning and expedited scanning are proposed accordingly. Prioritized scanning estimates the carrier qualities from the historical reports in the neighboring area. According to the estimated carrier qualities, a high priority is assigned to a carrier with better carrier quality. On the other hand, expedited scanning also estimates the carrier quality, but it jointly considers carrier correlations and spatial correlations. A dynamic estimation method is proposed to further enhance the estimation accuracy. Based on simulation results, the proposed algorithms can provide an average gain between 50% to 75% compared to the default scanning method when the neighbor distance is between 10 and 50 meters.1327641 bytesapplication/pdfen-US換手掃描多載波ScanningMulti-Carrierthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/252872/1/ntu-100-R96942120-1.pdf