混合式毫微微蜂巢式基地台網路之資源配置與分群方法

Abstract

To enhance indoor coverage and quality of service in both residential and enterprise environment, femtocells (FCs) have been proposed as a solution due to its low power consumption and being an end-user deployed base station. A FC can either share or be on a separate carrier from the macro-network. Due to high density of femto base station (fBSs), many challenges have not been sufficiently addressed such as resource allocation and interference management. The interference intensity mainly comes from the use of different access mode of fBS, which are closed access mode which permits only authorized subscribers to use the fBS and open access which allows all users to connect to the fBS. To gain the benefit of deployment of fBS for an enterprise environment, hybrid access mode has been selected to serve closed subscriber group (CSG) femto users and non-closed subscriber group (non-CSG) femto users. In this way the hybrid fBS may provide different service levels to femto users (FUEs) that are subscribers and non-subscribers. In this work we consider hybrid access mode which allows non-CSG users to connect to the fBS with limited resources. We propose a centralized power allocation (CPA) scheme where we perform resource allocation that reserves resources for non-subscribers using geometric programming (GP) and a novel sub-optimal clustering scheme in order to maximize the uplink (UL) capacity for non-CSG users. In addition, an admission control condition constraint is imposed on non-subscribers. Moreover, we propose a gaming-based distributed power allocation (GDPA) based on a non-cooperative game which converges to the Nash equilibrium (NE). We prove the existence of pure strategy Nash equilibrium of the non-cooperative game. The GDPA scheme tries to find the uplink power that will maximize the utility function based on the distance between the serving fBS and the FUE. Numerical results are presented and suggest the adoption of the proposed schemes.

為了提升住宅和企業內部環境的服務範圍和服務品質，毫微微型細胞 (femtocells)已被視為一個解決方案，因為它可以提供低功率耗損且讓使用者自行佈署的特性。此外，毫微微型細胞可以被允許與巨細胞網路 (macro network)使用相同的載波頻率或是不同的載波頻率。在一個具有高緻密毫微微型細胞佈署的傳輸環境中，資源配置和干擾管理是一個重要的研究議題，其中干擾主要來自於使用不同的存取模式的毫微微型細胞。若毫微微型細胞運作在封閉存取模式 (closed access mode)指的是只允許擁有子載波使用權的使用者來和毫微微型細胞做連結;而在開放存取模式 (open access mode)指的是所有使用者皆可和毫微微型細胞來做連結。 為了獲得毫微微型細胞在企業內部環境建置的好處，混合式存取模式 (hybrid access mode)可以考慮被系統所採用，該模式可以同時服務封閉式用戶群組 (closed subscriber group)毫微微型細胞內的使用者和非封閉式用戶群組(Non-closed subscriber group)毫微微型細胞內的使用者。此外，當毫微微型細胞運作在混合式存取模式，可以提供封閉和非封閉式使用者間不同的服務層級。 在本論文中，我們考慮毫微微型細胞運作在混合式存取模式，且僅允許非封閉式使用者使用連結的毫微微型細胞的部分限制資源。為了最大化非封閉式用戶群的上鏈傳輸容量，本論文提出了一種集中式的功率配置方式，為非封閉式用戶群使用者進行資源的分配，其中使用了幾何規劃（geometric programming）和一種新穎的次佳化分群策略。此外，我們也考慮非封閉式使用者允入控制條件 (admission control condition) 的限制。本論文還提出一個在賽局理論架構下的分散式功率配置演算法。其中利用了非合作式的賽局（non-cooperative game）理論及其納什均衡 （Nash equilibrium）的收斂特性。本論文針對在非合作式的賽局中，證明純策略（pure strategy）納什均衡的存在。我們所設計的功率配置演算法主要是根據毫微微型細胞與其服務的用戶之間的距離分配上鏈的功率，以最大化效益函數（utility function）。分析結果顯示，我們提出的資源與分群演算法能夠有效地改善系統的整體效能。