Performance Implication of Environmental Mobility in Wireless Networks

Environmental mobility refers to the ambient motion of people, vehicles and other objects in the vicinity of wireless communication. Whereas the effect of mobility of transmitting and receiving radios has been widely researched, the impact of environmental mobility has been relatively unexplored in wireless networks. In this paper, we present a systematic study to analyze the effect of environmental mobility on wireless link behavior and protocol performance using measurement, analysis, and simulations. Measurement data from channel traces was collected to isolate and quantify the effects of environmental mobility on the channel performance. Efficient models were developed to explain the observed behavior and integrated with network simulation to enable protocol level analysis under such dynamics. We found that the class of protocols that maintain state or have memory but are otherwise agnostic of the channel operations fare poorly by acquiring incorrect information about the channel and are not able to adequately exploit durations where channel conditions are good. Two case studies at different layers of protocol stack are used to quantify such behavior to show that protocol perform maybe as much as 20-50% below their expected performance. To remedy this situation we present a cross layer optimization scheme, called Recovery from Earlier Good State (REGS), that allows protocols to become aware of the underlying channel operations. We show that use of REGS together with existing optimizations can improve throughputs in the presence of EM by more than 100%.