SPECTRUM SHARING OPPORTUNITY FOR LTE AND AIRCRAFT RADAR IN THE 4.2 - 4.4 GHZ BAND
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The Federal Communications Commission (FCC) states that America is facing a spectrum crunch and there is no easy way to meet this increasing demand, hence spectrum sensing and sharing has gotten significant attention in the Spectrum Com- munity. Spectrum is an increasingly scarce natural resource which needs to be used to the fullest. Using modern techniques, spectrum bands can be reused such that they do not interfere with the current users in a band. There are many bands in the RF Spectrum which are underutilized and can be reused in the space-time domain. A number of bands have been recognized as candidates for spectrum sharing. In this dissertation, we consider the 4.2 − 4.4GHz band which is dedicated for used by the radar altimeter fixed on aircraft to measure their elevation above the earth’s surface. This spectrum is currently underutilized and with care can be shared with other technologies. This thesis examines the current use of this spectrum as a func- tion of time and location and presents a methodology for assessing whether harmful interference is experienced by either the incumbent radar usage or by a proposed wireless secondary broadband user. However, this band is a potential “safety of life” spectrum which is used by aircraft during landing and takeoff. Improper sharing of this band could cause interference at the radar, which would result in false attitude detection by the radar. Because of its advance technology, LTE should can be a good sharing candidate for this sensitive band. We propose sharing of this band with small cells (perhaps inside buildings) in urban and/or suburban areas, where there is a high demand for LTE and the attenuation from the environment is high enough to cause less interference at the radar altimeters. In this thesis, we propose to detect the aircraft (i.e. the altimeter radars) us- ing the Automatic Dependent Surveillance Broadcast (ADS-B) data which is broad- casted by an aircraft. This aircraft detection mechanism helps us to take intelligent sharing approaches with LTE using the space-time domain. Since the performance of the radar altimeter is safety-of-life critical, a deep understanding of co-existence between these systems is necessary to evaluate whether sharing is feasible. Given the availability of historical ADS-B data, what we believe is an appropriate analysis of Chicagoland has been done to propose implementation of a mix of Exclusion and Coordination zones in this area in the space-time domain. The novelty of this work is to develop spectrum sharing opportunities with radars which are highly transient and their locations are unpredictable due to emergency or traffic or weather. This thesis presents a method for evaluation of the potential for spectrum sharing between the ground-based LTE systems and commercial radar altimeters.