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Femtocell發展的介紹以及Covariance調整式適應性天線應用於該系統的數學分析
Femtocell Deployment Analysis and Methodology of Using Covariance Adjustment Adaptive Array
摘要
於WCDMA中配置Femtocell最近引起廣泛的討論。統計顯示：有超過50%的語音電話與超過70%的數據傳輸發自室內，這建議了安裝一基地台於室內，並以寬頻用internet的方式連接至Macrocell以分擔Macrocell的資源，如此可提供更有效的服務且節省整體設置費。因目前的3GPP的規範系統業者Macrocell與Femtocell必須使用同一載波頻率，所以Femtocell的配置必定會有同通道干擾，特別是當行動台接近Femto BSR時，因為CDMA”near-far”的power control的設計會使得Femtocell的BSR會因增加Macrocell的發射功率與其相互干擾，如此在Femtocell的房屋週圍形成一黑區，使得行動台無法交替至Femto。Alcatel-Lucent有提出一auto-configuration的辦法，由Femto依狀況自動調整其發射功率，模擬顯示該項設計使得同載波的Femtocell配置的系統是可行的，但若Femto與Macro的距離小於50米，則房屋內與週遭的某些部分仍會出現黑區（Black Zone）。智慧型陣列天線的構想被他們提出，為未來可改善的方向，該設計可使得Macro與Femto的天線增益可有效的做方向性的控制，使房子內與四週不形成黑區。目前各公司與學術界最亦廣泛的討論此種應用，本人早於1991年即提出一MCA Adaptive Array-用於CDMA系統中，可轉應用於Femtocell系統的配置。本研究在探討MCA Adaptive Array應用於Femtocell系統時，涵蓋率的數學分析的方法做討論，以提供未來模擬之探討。
並列摘要
The Femtocell deployment in WCDMA system has addressed great attention recently. The statistics shows that over 50% voice call and over 70% data traffics were originated from indoors. This suggests installation a Base Station Router in house connected to Macrocell by internet to share the loading of the Macrocell. Since current regulation, Macrocell system operation is confined in a single carrier frequency, the deployment of Femtocell will cause co-channel interference, especially when the mobile user is approaching the Femtocell the near-far set-up of the CDMA system would tend to increase the interference between Macrocell and Femtocell. This would cause Black zone around house that would prevent the mobile user handover to the Femtocell. To alleviate this problem, Alcatel-Lucent had planned a system that would automatic ally adjust the Femtocell's transmitting power. The performance is adequate to allow the deployment of Femtocell under the same carrier condition. Still, black zone appears in some part of the house when Femtocell BSR is close to Macrocell base station. Smart antenna has the advantage to intelligently adjust its beam so as to restrict the transmitting power of the Macro cell and Femtocell in certain direction so SINR can be controlled. Therefore, both industrial side and academic side had a great deal of research discussions toward this topic during the last few years. In this paper, we had proposed a MCA adaptive array system applied to the Femtocell deployment in an effort to solve the problem as suggested by Alcatel-Lucent. MCA adaptive Array is a method proposed by author in 1991 to be used in a common CDMA system. It would be adequate to impose such strategy to Femtocell deployment so as to eliminate the black zone. The strategy and coverage simulation method will be described for use in Alcatel-Lucent's simulation set-up for future simulation purpose.