Abstract—It is critical to understand the effect of wireless interference so that we can better utilize the spectrum through dynamic allocation methods. This paper presents the results of an experimental study done to characterize UDP performance in wireless networks in the presence of interference. We have carried out experiments in a Shielded Room facility using three different interference sources. A controlled interference source was used to generate continuous interference along with two known interference sources: a microwave oven and a FHSS phone. The impact of these interference sources on UDP has been quantified. The results obtained from experiments done inside the Shielded Room are compared with results from those done outside. The implications of using the Shielded Room as an experimental environment are discussed.

Abstract—This paper describes the development, deployment and early results of a long-term, wide-band (30 MHz - 6 GHz) spectrum observatory system focused on downtown Chicago and the immediately surrounding areas. Previous short term studies have indicated that more than 80% of the spectral capacity may be unused, even in United States urban centers. The goals of this research effort include the validation of these early results, the understanding of trends in spectral usage over long periods (years), the observation of usage patterns and anomalies, and the detection of the positions of spectral "holes" in time and space. The current status in the attainment of these goals will be shared in this paper. This information, once obtained, vetted and appropriately analyzed will be extremely useful in the development of cognitive radios and other dynamic access network systems, and in the proper establishment of policies and regulations to govern the deployment of such systems.

Abstract—This paper describes research on the development of an appropriate support structure for the analysis of the spectral environments to support the successful deployment and utilization of a cognitive radio system in specific high value spatial domains (e.g. urban centers). Specifically the paper discusses the opportunity to use a system of spectrum observatories augmented by wireless sensor networks to provide guidance to the discrete radios within a cognitive radio system on the most likely available spectral channels and bands. Toward this end, the paper separates and characterizes the spectral opportunity into four distinct classes. The paper also discusses four criteria for identifying and separating spectral bands into these classes.

Generic implementation requirements for a Spectrum Observatory are identified and illustrated with the embodiment at IIT’s Chicago campus. The paper discusses various academic and research opportunities afforded by the availability of a
Spectrum Observatory. Finally, the potential for the full deployment of a “spectrum traffic” system is discussed along with the requirement for continuing research efforts.

Abstract—Interference temperature is a measure of how well a radio operating with a particular protocol and modulation scheme can tolerate interference in its spectrum space. We consider this tolerance metric for the IEEE 802.11 protocol for
wireless networking. In experiments with off-the-shelf devices in the laboratory, we characterize the tolerance of the protocol to interference at various frequencies and power levels. Using the results of the experiment, we compute the interference temperature limit that the system will tolerate. We find that the interference temperature limit of the devices is much lower than the upper bound predicted by theory. The interference temperature limit of the protocols is not proportional to the data capacity, hence factors in the physical implementation play an important role in the robustness of the channel.