Quantifying Device-to-Device Data Transfer in 802.11 Wireless Networks

摘要

Opportunistic contacts can be very short-lived, i.e., they usually last for a few seconds to several minutes. During the short connection window of an opportunistic contact, it is important to maximize the data transfer between the nodes. The amount of data that can be transferred during an opportunistic contact (i.e., contact capability) will depend on the link layer connection establishment delay, IP address acquisition delay as well as on the data throughput. If the opportunistic network is aimed for service provisioning, the delay of the service discovery phase is also needed to be taken into account while defining the capability of the contact. Moreover, the wireless environment where the opportunistic contacts take place, can influence the overall capability of the opportunistic contacts. In the thesis, we get the opportunity to put emphasize on all these factors while quantifying the opportunistic contacts (i.e., device-to-device data transfer) in indoor 802.11b Wi-Fi networks (Infrastructure mode).This thesis makes several original contributions. First, we carefully design the indoor wireless testbed and to facilitate the experiments we build a Service Browser and Service Publisher application. Second, we conduct a site survey in the testbed area to gain an understanding on the indoor RF wave propagation characteristics. Third, we perform experiments, where we collect traces during the link-layer connection establishment, IP address acquisition and service discovery phases of opportunistic contacts. Using the collected data, we measure the delays of the different events/steps that take place during the phases mentioned above. Furthermore, we run experiments to investigate the throughput performance of data transmission between the nodes when TCP is used as the transport layer protocol and thus to check the suitability of TCP in opportunistic networks.