在日趨增加的頻寬需求之下，傳統的細胞網路架構已然漸漸不敷使用，增設小基地台成為一種可能的解決方案，增設的小基地台雖可減輕大基地台的流量，但若採用傳統以接收訊號強度為判斷基準的基地台選擇機制，分擔流量的效果相當有限。為有效提高小基地台的負載量，廣受當前學界討論的做法是透過虛擬增加來自小基地台的訊號強度，來提高連線到小基地台的使用者數量，但與此同時選擇連線到小基地台的使用者所受到來自於大型基地的干擾情形將十分的嚴重，並且此選擇機制未將各基地台連線的人數列入考量機制當中，對整體網路的分流效果有限。我們提出了一種考量基地台連線情況的細胞選擇機制，該機制根據各基地台連線人數與基地台所能負載的流量進行動態分流。根據模擬的結果，所提出的選擇機制能達到更好的連線速度並且降低連線被阻擋的機率。

The notion of small cells has been widely discussed because it can improve the network capacity and coverage by shifting mobiles from macro base stations (BSs) to the low-power pico BS. In the existing cell association scheme, known as cell range expansion (CRE), a constant cell association bias is employed. Without taking the BS load into consideration, a BS might still be overloaded or underloaded that in turn causes low resource utilization rate or high blocking probability, respectively. In this work, we propose a load-based cell selection scheme to address the aforementioned issues. An adjustment function is introduced to properly determine the cell association bias based on the individual BS load. Using 3GPP long term evolution advanced (LTE-A) compliant parameters the simulation results show that the proposed load-based cell selection scheme achieves significant performance gains in terms of long term average rate and call blocking probability, as compared with the conventional cell association scheme using the constant bias.

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