在區域多點資訊分送服務 (Local Multipoint Distribution Service, LMDS) 系統下，同頻干擾 (co-channel interference) 是個限制系統容量 (capacity) 重要因素。為了降低同頻干擾的影響，在這篇論文中我們提出了一個旋轉基地台的概念。利用此旋轉基地台概念所形成的新細胞式架構可以增加系統的效能 (performance)，但不需增加系統設備的費用。 另外，本文介紹頻率重複使用 (frequency reuse) 的觀念，比較三個頻率重複使用因子 (reuse factor) 的系統。結果顯示較低頻率重複使用因子的系統可以得到最佳的涵蓋比率 (coverage ratio) 效能。較高頻率重複使用因子的系統可以得到較佳的頻寬效率 (bandwidth efficiency) 效能，也就是說，用戶的數目可以增加。此外，利用旋轉基地台的概念不僅可以增加涵蓋比率的效能，也可以增加頻寬效率的效能。所以在LMDS的系統下，旋轉基地台是個非常有用的方法來降低同頻干擾，並且增加系統的頻寬效率。 In Local Multipoint Distribution Service (LMDS) system, co-channel interference is the limiting factor in determining the capacity. In order to reduce co-channel interference, we introduce the concept of rotated base station (BS) architecture. The proposed architecture with rotated BS can enhance the system performance without raising the cost. We also introduce the frequency reuse concept. We compare systems with reuse factor = 1, 2 and 4. The results show that the lower reuse factor system can get the better performance of coverage ratio. The higher reuse factor system can get better performance of bandwidth efficiency, that is, the number of subscribers can increase. Furthermore, the rotated base station concept can get better performance of coverage ratio and bandwidth efficiency. Therefore, the base station rotation is a very useful concept to reduce co-channel interference and increase bandwidth efficiency in the LMDS system.
