23-06-2012, 05:36 PM
A Measurement-Driven Anti-Jamming System for 802.11 Networks
[attachment=25335]
Abstract
Dense, unmanaged IEEE 802.11 deployments tempt
saboteurs into launching jamming attacks by injecting malicious
interference. Nowadays, jammers can be portable devices that
transmit intermittently at low power in order to conserve energy.
In this paper, we first conduct extensive experiments on an indoor
802.11 network to assess the ability of two physical-layer functions,
rate adaptation and power control, in mitigating jamming.
In the presence of a jammer, we find that: 1) the use of popular
rate adaptation algorithms can significantly degrade network
performance; and 2) appropriate tuning of the carrier sensing
threshold allows a transmitter to send packets even when being
jammed and enables a receiver to capture the desired signal.
INTRODUCTION
THE WIDESPREAD proliferation of IEEE 802.11
wireless networks makes them an attractive target for
saboteurs with jamming devices [1]–[4]. This makes the defense
against such attacks very critical. A jammer transmits
electromagnetic energy to hinder legitimate communications
on the wireless medium. A jamming attack can cause the following
effects in an 802.11 network: 1) due to carrier sensing,
cochannel transmitters defer their packet transmissions for
prolonged periods; and 2) the jamming signal collides with
legitimate packets at receivers.
SYSTEM GUIDELINES FOR RATE ADAPTATION
Rate adaptation algorithms are utilized to select an appropriate
transmission rate as per the current channel conditions.
As interference levels increase, lower data rates are dynamically
chosen. Since legitimate nodes consider jammers as interferers,
rate adaptation will reduce the transmission rate on legitimate
links while jammers are active. Hence, one could potentially
argue that rate control on legitimate links increases reliability by
reducing rate and can thus provide throughput benefits in jamming
environments.
SYSTEM GUIDELINES FOR POWER CONTROL
Next, we examine whether tuning power levels can help cope
with the interference injected by a jammer. If we consider a
single legitimate data link and a jammer, incrementing the transmission
power on the data link should increase the signal-to-interference-
plus-noise ratio (SINR) of the received data packets.
Thus, one could argue that increasing the transmission power is
always beneficial in jamming environments [17].
CONCLUSION
We design, implement, and evaluate ARES, an anti-jamming
system for 802.11 networks. ARES has been built based
on observations from extensive measurements on an indoor
test-bed in the presence of random jammers and is primarily
composed of two modules. The power control module tunes
the CCA thresholds in order to allow the transmission and
capture of legitimate packets in the presence of the jammer’s
signals to the extent possible.
[attachment=25335]
Abstract
Dense, unmanaged IEEE 802.11 deployments tempt
saboteurs into launching jamming attacks by injecting malicious
interference. Nowadays, jammers can be portable devices that
transmit intermittently at low power in order to conserve energy.
In this paper, we first conduct extensive experiments on an indoor
802.11 network to assess the ability of two physical-layer functions,
rate adaptation and power control, in mitigating jamming.
In the presence of a jammer, we find that: 1) the use of popular
rate adaptation algorithms can significantly degrade network
performance; and 2) appropriate tuning of the carrier sensing
threshold allows a transmitter to send packets even when being
jammed and enables a receiver to capture the desired signal.
INTRODUCTION
THE WIDESPREAD proliferation of IEEE 802.11
wireless networks makes them an attractive target for
saboteurs with jamming devices [1]–[4]. This makes the defense
against such attacks very critical. A jammer transmits
electromagnetic energy to hinder legitimate communications
on the wireless medium. A jamming attack can cause the following
effects in an 802.11 network: 1) due to carrier sensing,
cochannel transmitters defer their packet transmissions for
prolonged periods; and 2) the jamming signal collides with
legitimate packets at receivers.
SYSTEM GUIDELINES FOR RATE ADAPTATION
Rate adaptation algorithms are utilized to select an appropriate
transmission rate as per the current channel conditions.
As interference levels increase, lower data rates are dynamically
chosen. Since legitimate nodes consider jammers as interferers,
rate adaptation will reduce the transmission rate on legitimate
links while jammers are active. Hence, one could potentially
argue that rate control on legitimate links increases reliability by
reducing rate and can thus provide throughput benefits in jamming
environments.
SYSTEM GUIDELINES FOR POWER CONTROL
Next, we examine whether tuning power levels can help cope
with the interference injected by a jammer. If we consider a
single legitimate data link and a jammer, incrementing the transmission
power on the data link should increase the signal-to-interference-
plus-noise ratio (SINR) of the received data packets.
Thus, one could argue that increasing the transmission power is
always beneficial in jamming environments [17].
CONCLUSION
We design, implement, and evaluate ARES, an anti-jamming
system for 802.11 networks. ARES has been built based
on observations from extensive measurements on an indoor
test-bed in the presence of random jammers and is primarily
composed of two modules. The power control module tunes
the CCA thresholds in order to allow the transmission and
capture of legitimate packets in the presence of the jammer’s
signals to the extent possible.