Lessons Learned Constructing the NG-Mesh Wireless Test-Bed

Abstract

<p>This thesis presents the lessons learned from building an IEEE 802.11 wireless mesh network (WMN) test-bed. Each network node consists of a Linux processor with multiple IEEE 802.11b/g transceivers operating in the 2.4 GHz band. Each transceiver consists of a medium access control (MAC) and base-band processor (BBP) in addition to a radio. A device driver was modified to control some of the key transceiver functions. The test-bed's Wi-Fi interfaces can be programmed to implement any mesh communication topology. All Wi-Fi interfaces use omni-directional antennas and the IEEE 802.11b operation mode.</p> <p>The test-bed design is easily extendable to incorporate newer Wi-Fi technologies. Measurements of co-channel interference in each Wi-Fi channel including received signal strength (RSS) and signal-to-interference-and-noise ratio (SINR) are presented. The AutoMin algorithm was developed in order to use the captured physical layer (PHY) metrics to avoid Wi-Fi congestion during test-bed operation. A comparison of a software-based spectrum analyzer to a commercial one is described. Key Wi-Fi functions in the Ralink driver source code are explored in depth. The compliance of the Ralink chip-set to the IEEE 802.11b spectral mask was verified. The maximum driver-induced retuning rate for the popular Ralink radio was found experimentally. This data can be used to optimize the performance of IEEE 802.11 WMNs.</p>