Rate-aware Power Control Mechanisms with Busy-tone Channels in Multi-rate Carrier-sensing Wireless Environments

• Main Authors: Yao, Sheng-Kai, 姚勝凱
• Other Authors: Lin, Ting-Yu
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/v56snd

碩士 === 國立交通大學 === 電信工程研究所 === 106 === With the rapid development of wireless mobile networks, the number of wireless network equipment also grows exponentially. Considering an enormous amount of data traffic, packet collision avoidance has become an important yet challenging issue. IEEE 802.11 uses CSMA/CA mechanism to avoid collisions, and RTS/CTS is further used to protect the data being transmitted. However, in such wireless networks, successful transmission depends heavily on the perceived SINR (Signal-to-Interference-and-Noise Ratio) at the receiver. We observe that using maximum transmission power doesn’t always yield the best result. Rather, it leads to redundant transmitter power, wasting energy resources, and even causing a greater interference to neighboring nodes. Coupled with RTS/CTS virtual carrier sense, the IEEE 802.11 protocol suffers from serious exposed terminal problems. As such, we suggest to take the environmental status of the receiver into account, and properly limit transmission power that affects neighboring nodes. In this thesis, unlike traditional binary decision of transmitting or deferring, we propose a rate-aware power control algorithm which works as follows. Receiver uses the current transmission rate (from transmitter) to calculate the minimum required SINR for a successful transmission, and sends busy-tone signal to the surrounding nodes. The surrounding nodes utilize the busy-tone signal to estimate how much power can be used without affecting the reception of other nodes and adjust their transmission power accordingly. Our proposed algorithm attempts to maximize the channel’s spatial usage, thus effectively increasing the overall network throughput. We adopt the Wi-Fi model in NS3 to simulate our proposed algorithm based on IEEE 802.11ac. We conduct experiments for different node densities, analyze the network throughput and compare the performance with other existing algorithms. The experimental results show that our proposed algorithm can dynamically adjust the transmission power to adapt to the environmental changes while maintaining excellent network throughput and low collision rate. Furthermore, it effectively increases the number of simultaneous successful transmissions.