DAPnet: a testbed for measuring the impact of transmission parameters on an 802.11 based dense access point network

There are several parameters that influence the performance of a wireless network. In this thesis, we investigate the impact of minimum size of contention window (cwmin), transmission power, and transmission rate on a dense multiAP network. We have built a testbed called DAPnet for this experiment. DAPnet lets us change cwmin, cwmax, transmission rate, transmission power and operating channel of the nodes in the network remotely. The testbed was deployed at the Coordinate Science Lab (CSL) which is a research center at the University of Illinois. This testbed consists of 40 computing devices equipped with ath9k_htc based USB wireless cards. We studied the control flow path of the Linux Networking and ath9k_htc driver to implement the testbed. The system lets us change the parameters of all the transmitting machines by running commands remotely from a controller machine. Our experimental results show how different combination of rate and minimum size of contention window affects the throughput and packet drop rate of the dense access point network that we set up in CSL. We also show a small-scale ideal layout for dense-AP network that can improve the reliability and throughput of a dense-AP network