小型基地台功率嗅探控制技術研究

Abstract

近年來利用小型基地台來提升網路系統容量是最好的方法之一。小型基地台的優點在於可以減輕大型基地台的負擔，這麼一來大型基地台也可以不用分享自己的頻寬。在一個很多用戶都在移動的系統之下，雖然這個系統很常使用Microcell，但是有另一個價格較低的選擇，那就是家庭基站(Femtocell) [1]。

雖然小型基地台對行動網路系統來說的幫助很大，但是要設計出一個最佳的系統也必須面對許許多多的挑戰。因為有很多的小型基地台並不是隨時都在服務用戶但是卻又處於開機狀態，這樣會出現浪費能源的情形，且對環境也造成一定的影響。根據ABI的研究 [2] ，2014年家庭基站的出貨量會成長約350%，且在2013到2018年之間複合年均增長率也會達約198%。去年年底總共有大約3600萬台家庭基站被賣出，且每個基站消耗的功率為12瓦。這樣總合起來每個基站所消耗的能源會大約造成205萬噸的二氧化碳排放量。 在考量這些對環境影響與不犧牲基站傳輸功能與品質的情況下，設計出一個有效率的系統變得相當重要。雖然有很多個提案，但是幾乎沒有一個提到要最佳化家庭基站裡面嗅探器(Sniffer)的啟動與持續時間。 在這個論文裡面我們會探討家庭基站的技術層面且解釋目前在商業界裡面的狀態。我們會利用在這論文裡提到的家庭基站的空閒模式(Idle Mode) 來減輕基地台的負擔，並且估計出家庭基站裡面嗅探器最佳化的啟動與執行時間。系統環境會經過模擬來找出最佳化的時間。

Small-Cells are nowadays one of the best options to increase the network system capacity. Small cells Base Stations are perfect for the provision of high data rate services because it offers the localization of radio signals, so that the Macrocell doesn’t have to share its bandwidth. In a network with nomadic users typically the network system is increase by using Small Cells in the form of microcells, but a less expensive alternative are the Femtocell concept [1]. Even though small cell networks can increase the cellular network capacity there are still many challenges to overcome to design an optimal system. Most of small cells are only sporadically serving users and excessive waste of energy occurs due to the small cell’s radio system that is optimized for maximum load. This excessive waste of energy will become a vital issue in the future affecting environmental sustainability. According to ABI Research [2], the number of Small Cells shipments is likely to increase by 350% in 2014 and a Compound Annual Growth Rate (CAGR) of 198% is estimated between 2013 and 2018. By the end of last year an estimated of 36 million Small cells were sold; each Small Cell requires a power of 12W (105.12 kWh/annum) [3], the total energy consumption of all Small Cells amount to 3.784 × 109 kWh/annum; which means that the operation of Small Cell is likely to produce 2.05 million tons of CO2 per year.

To address these particular issues, efficient methods for reducing the Small Cell energy consumption resulting from processing signal as well as transmission without sacrificing functionally and efficiency are required. Different types of idle mechanisms where proposed. However, none of these mechanisms takes under consideration the Small Cell radio sniffer’s active time under a centralized control system.

In these thesis we overview the technical and business arguments for Small Cell and describe the state of the art on each front. We make used of proposed idle mode techniques in traffic offload circumstances to develop a new control mechanism for the Small Cell based on the sniffer. Simulations have been made to quantify the performance of this solution.