Co-existence between unlicensed networks that share spectrum spatio-temporally with terrestrial (e.g. Air Traffic Control) and shipborne radars 1 in 3 GHz band is attracting significant interest. Similar to every primary-secondary coexistence scenario, interference from unlicensed devices to a primary receiver must be within acceptable bounds. In this work, we formulate the spectrum sharing problem between a pulsed, search radar (primary) and 802.11 WLAN as the secondary. We compute the protection region for such a search radar for a) a single secondary user (initially) as well as b) a random spatial distribution of multiple secondary users. Furthermore, we also analyze the interference to the WiFi devices from the radar's transmissions to estimate the impact on achievable WLAN throughput as a function of distance to the primary radar. DRAFT 3 and b) Military/commercial sharing between military radars and commercial communication systems to preserve radar capabilities while meeting the need for increased capacity of commercial networks. In [6]-[8], the authors study coexistence between radar and a cellular base station. The co-existence strategy espoused is variable secondary transmit power assuming a maximum tolerable interference at the radar. Further, the authors consider only one sharing scenario in which SU is perfectly synchronized with radar rotation (a very impractical assumption). The limitations of this analysis is thus apparent -it does not explore at any depth, how the radar's interference tolerance is determined based on the system parameters and geometry considerations. Similarly in [4] , temporal variations of radar antenna's main lobe is exploited to support more white space users when their location is not within the main lobe. In [9] , spectrum sensing is combined with database approach to create a hybrid spectrum sharing technique. The authors in [12] study the potential for secondary LTE usage in 2.7-2.9 GHz radar bands for different scenarios such as home eNodeB (HeNB) at street levels or in high-rise buildings, macro LTE transmitters and so on. A fixed Interference-to-Noise ratio (INR) of -10 dB is specified for sharing without any discussion on radar performance. The analysis does not consider radar rotation and mostly focused on single-user sharing with radar. While the case of multiple SU is considered, it is done so under an unrealistic assumption that all users are at the same distance from radar. Finally, spectrum sharing between a MIMO radar and a wireless communication system is analyzed in [13] . Their interference mitigation approach is shown to eliminate wireless interferences from main/side lobe while maintaining target detection performance. Some U.S. DoD studies for co-existence with radars operating in the 2700-2900 MHz and 5250-5850 MHz bands [18] , [19] have also been conducted. Protection criteria against external interference is determined through experimental measurements by injecting three types of unwanted communications waveform emissions -continuous wave, CDMA-QPSK, and TDMA-QPSK. In [20] , the authors evaluate interference from broadband communication transmitters such as WiMax to WSR-88D next-generation weather radar (2700-2900 MHz). A computation model for calculating aggregate interference from radio local area networks to 5-GHz radar systems is provided in [21] . The analysis methodology is based on using point to point path loss models between radio networks and radar as well as other link parameters such as antenna gains and frequency-dependent rejection [16] , [17] . Our major contribution in this work is a complete characterization of Radar -WiFi coexistence as a function of all relevant system parameters and design constraints/objectives. First, the maximum tolerable interference from WiFi networks to radar is estimated for both a a) single WiFi network and b) a (random) spatial distribution of multiple WiFi networks. Depending on how much information about radar is available to secondary (WiFi) networks, various sharing scenarios are considered, resulting in different protection distances. Second,the (time-varying) interference from radar to WiFi networks is modeled and achievable secondary link throughput is estimated.
In REF , the authors consider the coexistence between a search radar (2700-2900 MHz) and WLAN systems, and provide the analysis to find a protection region around radar for single and multiple interferers.
Spectrum Sharing Between A Surveillance Radar and Secondary Wi-Fi Networks
IEEE Transactions on Aerospace and Electronic Systems
IEEE Transactions on Aerospace and Electronic Systems
Computer Science Mathematics