多媒體分碼多重進接細胞網路之功率及允入控制

Abstract

本論文主要在研究多媒體分碼多重進接網路的功率控制及允入控制，在此研究中，使用者可以有不同的資料率及服務品質要求（以位元能量對干擾之比值來表示）。在集中式功率控制方面，本論文推導出最佳之合適功率（能滿足所有使用者服務品質要求之功率），此功率可以藉著解一組線性方程式而得到。在分散式功率控制方面，本論文證明了只要系統存在有合適功率，則所提出的分散式功率控制演算法均能找到一組解。此外，本論文亦提出一個僅作部分鏈路增益量測之類集中式功率控制演算法來加速找到合適功率，數值結果顯示其找到合適功率的速度會增快許多。 有關多媒體分碼多重進接網路的允入控制技術最近在[13,14]中被提出，有考慮及未考慮活動力因素之允入法則和系統容量分別被推導出來，由於在他們的分析中，自己的發射功率被視為干擾的一部份，因此其所得到的為系統容量的下界；若多路徑干擾分量可以完全被解析出來，則吾人可以得到一個較樂觀的系統容量上界，本論文即針對此推導出最佳之功率配置及能滿足所有使用者服務品質要求的允入法則，從數值結果可以發現其系統容量確實可以獲得明顯之提升。數個可以確保延遲界限要求的進接控制策略亦分別被提出，模擬結果顯示這些策略可以使系統接受更多的連結。

We study in this dissertation both power control and admission control for multimedia CDMA networks. In our study, users can have different data rates as well as different quality of service (QoS) requirements characterized by bit energy-to-interference ratios. For centralized power control, we derive an optimal feasible power set which can be obtained by solving a set of linear equations. For distributed power control, we prove that, as long as there are solutions of power levels for all users to meet their QoS requirements, the proposed distributed power control algorithm can always find one. A quasi-centralized power control algorithm with partial link gain measurements is proposed to speed up the process in finding a feasible power set. In the algorithm, a base station measures the link gains for all mobiles connected to it. Numerical results show that quasi-centralized power control can find a feasible power set much faster than distributed power control. An admission control technique for multimedia CDMA networks has recently been proposed [13,14] to provide integrated services in a wireless packet network. Admission criteria and system capacities with and without considering user activity factors were derived. The analysis gives a lower bound of system capacity because a user's transmitted power is considered part of the interference to its own signal. In this dissertation, we present an optimistic upper bound assuming that there is no multipath fading or the energy of a signal in all multipath components can be fully resolved. An optimum power vector assignment and a simple criterion for all users to simultaneously achieve their quality of service requirements (in terms of bit energy-to-interference density ratios) are derived. We found from numerical examples that, compared with the lower bound given in [13,14], significant improvement can be obtained if multipath fading can be satisfactorily handled. Several access control schemes are also studied to guarantee delay bound requirements. Simulation results reveal that more connections can be further accommodated with access control.