負載感知多點協調傳輸在高密度異質性網路之效能分析研究

Abstract

本論文研究在高密度異質性網路的佈建下，運用負載感知技術後分析基地台間在下行時合作式傳輸的效能。在高密度異質性小型基地台的佈建下，會產生沒有使用者連接的閒置基地台，而我們所提出的方法是利用這些閒置基地台做合作式的傳輸來提升覆蓋率跟傳輸速度。在本論文的數學分析上，我們推導出此合作式傳輸之傳輸速率跟覆蓋率的上限和下限的表示式，而上限和下限的表示式能適用於多天線環境且非常貼近實際值，也直接的反應出系統效能增加的原因。接著，探討非正交多重接取跟合作式非正交多重接取技術在高密度異質性網路下行系統的覆蓋率，並分析是否有來自非正交多重接取技術的增益。本論文提出的策略研究都大幅地提升傳輸覆蓋率及傳輸速率，其效能分析皆被模擬結果所驗證。

In this thesis, we propose a load-aware approach to performing the downlink coordinated multi-point joint transmission (JT-CoMP) scheme in a dense heterogeneous cellular network consisting M tiers of different kinds of base stations(BSs). Inspiring from the fact that there could exist a considerable number of the void BSs without any users in a dense HetNet, the proposed load-aware JT-CoMP is able to coordinate the void BSs so as to enhance the downlink transmission of the non-void BSs. Using such a CoMP scheme, the fundamental upper and lower limits on the coverage and ergodic link throughput of a user with downlink MISO channel are accurately found in a low-complexity approximated form and they straightforwardly show that the load-aware CoMP scheme has the capability of significantly increasingthe coverage and ergodic link throughput of a user as long as the user intensity is not very much higher than the total intensity of the BSs. Afterwards, the downlink coverage performance of the HetNet with the non-cooperative and the proposed cooperative NOMA schemes is studied in order to understand how they are improved by the NOMA schemes. Numerical results validate the correctness of the analytical results and demonstrate the significant gains of the performance exploited by the proposed load-aware CoMP scheme.