LTE-A 蜂巢式系統下改善效能及負載轉移之中繼節點放置規劃

Relay Deployment for Capacity Enhancement and Load Transfer in LTE-A Cellular Systems

翁儷維(Li-Wei Weng)

指導教授 ： 黃啟富

國立中正大學/工學院/資訊工程學系/碩士(2013年)

摘要

在3GPP LTE-Advanced 網路中，提出中繼技術來提升系統效能以及擴大系統覆蓋範圍。由於細胞間的干擾(inter-cell interference)，LTE-Advanced網路具有細胞邊界用戶訊號品質不佳的問題。透過擺放中繼節點(relay node, RN)，將能解決此問題並且改善細胞邊界的效能。因此，如何將中繼節點擺放在適當的位置成為一個重要的議題。此外，當一個細胞(cell)內的用戶流量需求大於基地台(evolved Node B, eNB)所能提供的服務量時，會導致此細胞的流量負載(traffic load)過重。如果我們在負載過重的細胞(overloading cell)內擺放中繼節點，由於無線資源有限，使得細胞邊界的效能改善效果不佳，所以我們希望在考慮干擾、中繼節點佈建成本以及細胞流量負載的情況下，設計一個中繼節點擺放策略，除了能提升細胞邊界的效能之外，還能將負載過重的細胞其流量負載轉移到鄰近的細胞。在本篇論文中，我們一開始先對中繼傳輸鏈結(relay communication links)進行分析，再定義細胞邊界效能最大化的中繼節點擺放問題並且將問題公式化。隨後，我們證明此問題是NP-hardness的問題以及提出一個兩階段的啟發式演算法來決定中繼節點的擺放位置。最後，模擬結果顯示，我們的中繼節點擺放策略能夠提升細胞邊界的效能、達到負載轉移以及降低細胞邊界用戶無法被服務的機率。

關鍵字

放置 ； 中繼節點 ； LTE-A ； 效能改善

並列摘要

3GPP LTE-Advanced introduces relaying technologies to enhance system capac-ity and extend system coverage. One of the problems in LTE-Advanced is low sig-nal-to-interference-plus-noise (SINR) of cell edge users due to inter-cell interference. Deploying the relay nodes (RNs) can deal with this problem and improve the cell edge capacity. Thus how to find out the suitable locations for RNs is important. Moreover, when the overall traffic demands required by users are greater than the total capacity provided by evolved Node B (eNB) of a cell, the traffic load of this cell is overloading. If we deploy the RNs in an overloading cell, the cell edge capacity can-not be improved due to the limitation of radio resources. Therefore, we design a RN deployment strategy to enhance cell edge capacity and transfer the traffic load of the overloading cell to its neighboring cells by taking interferences, deployment budget of RNs, and traffic load of cell into consideration. In this paper, we first model and ana-lyze the capacity of relay communication links. Next, we formally define and formu-late a RN deployment problem which maximizes cell edge capacity. Then, we prove that this RN deployment problem is NP-hardness and propose a two-phase heuristic to determine deployment of RNs. The simulation results show that our RN deployment strategy can enhance the cell edge capacity, achieve traffic load transfer of the over-loading cell and reduce the outage probability of cell edge users.

並列關鍵字

Capacity enhancement ； Deployment ； Relay node ； LTE-A

參考文獻

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