| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 95 === When VoIP was in the initial developing stage, people thought it as a free service and did not care the voice quality too much. VoIP is more and more popular around the world and is going to replace a part of traditional telecommunication. The key that VoIP can keep gaining popularity in the future absolutely not lies in its cost effectiveness but in its the improvement of voice quality.
In recent years, multi-radio device has become more and more popular because its convenience and cost down of such radio modules. Multi-radio devices include fixed multi-radio devices (such as 802.11a/b/g multi-mode multi-radio gateway) and mobile multi-radio devices (such as 2G/3G/WLAN PDA and smartphone). The main purposes of multi-radio devices are to increase the total throughput, cost effectiveness, convenience, and the reliability. Because the cost of wireless network interface modules have been decreased rapidly in recent years, everyone should be able to afford such a mobile multi-radio device. In this thesis, we use duplicated parallel transmission to reduce the delay and packet loss condition, and then propose the Channel Selection Algorithm and the Channel Switching Algorithm deployed in multi-radio devices to improve the VoIP call quality by exploring the complementary properties among parallel channels.
In order to verify the performance of our algorithms, we execute the simulations in C language and use IEEE 802.11a as the wireless channel environment. The simulation results show that under the circumstances that the wireless channels quality is not too bad and the background traffic is not constantly heavy, the proposed multi-radio device system dose provide an acceptable VoIP call quality.
|
|---|
