181 research outputs found
Clearing the Rf Smog: Making 802.11 Robust to Cross-Technology Interference
Recent studies show that high-power cross-technology interference
is becoming a major problem in today’s 802.11 networks. Devices
like baby monitors and cordless phones can cause a wireless
LAN to lose connectivity. The existing approach for dealing
with such high-power interferers makes the 802.11 network switch
to a different channel; yet the ISM band is becoming increasingly
crowded with diverse technologies, and hence many 802.11 access
points may not find an interference-free channel.
This paper presents TIMO, a MIMO design that enables 802.11n
to communicate in the presence of high-power cross-technology
interference. Unlike existing MIMO designs, however, which require
all concurrent transmissions to belong to the same technology,
TIMO can exploit MIMO capabilities to decode in the presence
of a signal from a different technology, hence enabling diverse
technologies to share the same frequency band. We implement a
prototype of TIMO in GNURadio-USRP2 and show that it enables
802.11n to communicate in the presence of interference from baby
monitors, cordless phones, and microwave ovens, transforming scenarios
with a complete loss of connectivity to operational networks.National Science Foundation (U.S.) (NSF grant CNS-0831660)National Science Foundation (U.S.) (NSF grant CNS- 0721857)United States. Defense Advanced Research Projects Agency (DARPA ITMANET
Radar Interference Mitigation for Automated Driving: Exploring Proactive Strategies
Autonomous driving relies on a variety of sensors, especially on radars, which have unique robustness under heavy rain/fog/snow and poor light conditions. With the rapid increase of the amount of radars used on modern vehicles, where most radars operate in the same frequency band, the risk of radar interference becomes a compelling issue. This article analyses automotive radar interference and proposes several new approaches, which combine industrial and academic expertise, toward the path of interference-free autonomous driving
Multi-band OFDM UWB receiver with narrowband interference suppression
A multi band orthogonal frequency division multiplexing (MB-OFDM) compatible
ultra wideband (UWB) receiver with narrowband interference (NBI) suppression
capability is presented. The average transmit power of UWB system is limited to
-41.3 dBm/MHz in order to not interfere existing narrowband systems. Moreover, it
must operate even in the presence of unintentional radiation of FCC Class-B compatible
devices. If this unintentional radiation resides in the UWB band, it can jam the
communication. Since removing the interference in digital domain requires higher dynamic
range of analog front-end than removing it in analog domain, a programmable
analog notch filter is used to relax the receiver requirements in the presence of NBI.
The baseband filter is placed before the variable gain amplifier (VGA) in order to reduce
the signal swing at the VGA input. The frequency hopping period of MB-OFDM
puts a lower limit on the settling time of the filter, which is inverse proportional to
notch bandwidth. However, notch bandwidth should be low enough not to attenuate
the adjacent OFDM tones. Since these requirements are contradictory, optimization
is needed to maximize overall performance. Two different NBI suppression schemes
are tested. In the first scheme, the notch filter is operating for all sub-bands. In the
second scheme, the notch filter is turned on during the sub-band affected by NBI.
Simulation results indicate that the UWB system with the first and the second suppression
schemes can handle up to 6 dB and 14 dB more NBI power, respectively. The results of this work are not limited to MB-OFDM UWB system, and can be
applied to other frequency hopping systems
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