無線隨意網路之漸層式傳輸功率控制及繞徑協定實作

Abstract

在無線網路研究中，有許多為了增加多重傳輸數量和減少干擾影響的機制，而其中 傳輸功率控制機制是我們想要研究的部分。在本篇論文中，我們專注於如何在多跳通訊環境中運用傳輸功率協定於這些配備多個通道的無線傳輸設備，使之得到更高的系統效能。在單通道無線傳輸中，如果把傳輸端的傳輸功率調降，會導致網路的連結性較低並造成較長的路由路徑和較高的空間重複使用性，這兩個參數對於無線網路容量顯得非常重要。有鑑於此，在多通道網路的環境中，我們提出一個功率控制機制，他可以把整個網路架構分成多個網路，因此我們稱之為漸層式傳輸功率控制協定(GradPC)。在我們提出的漸層式傳輸功率控制協定(GradPC) 中，基本通道被設定預設的傳輸功率(無使用功率控制) ，而在其他非基本通道中，我們採用控制鄰近節點連接數之傳輸功率控制方式來實現漸層連結度。在GradPC 設定完所有無線介面的傳輸功率後，再配合相應的G-mcDSR 路由協定，選擇適當的傳送路徑和分配合適之通道。在本論文中，我們進一步實作GradPC 機制在依據CSMA 的ad hoc 環境中，藉由新增以及修改在Linux 平台上的路由程式。我們同時也顯示GradPC 在實際網路系統的效能，根據實測結果顯示藉由平衡選取較短路徑以及提高媒介使用率的GradPC 機制並使用對應的G-mcDSR 路由協定效果可以比其他協定要來的好。

While various power control techniques have been proposed to improve aggregate network throughput by reducing the interference impact and encouraging more concurrent transmissions in medium-shared wireless systems, we do not intend to devise new power control mechanisms. Rather, we investigate the interoperability of two performance-related parameters, transmit power and radio channel, in a wireless ad hoc network. In our previously proposed GradPC protocol, a base channel is designated to use default transmit power (no power control on this radio). For other non-base radios, we adopted neighbor-based power control techniques to tailor the connectivity degree for each radio channel. Imagine several superposed network topologies having gradational connectivity levels over multiple non-interfering channels, hence the name, gradational power control (abbreviated as GradPC), was given. A corresponding multi-channel routing protocol, entitled G-mcDSR, was devised to judiciously mix short and long hops over appropriate channels in a multi-hop path. In this thesis, we further implemented the GradPC protocols in a working CSMA-based wireless ad hoc network by modifying and adding modules to a router software on the Linux platform. Empirical results demonstrate that the proposed GradPC mechanisms along with G-mcDSR routing protocol outperform other strategies by imposing gradational power levels on radios to balance the requirements for short route and high medium utilization. From the prototyping experiences, we also show the efficacy of GradPC protocols in a real networking system.