254 research outputs found
Active Attack on User Load Achieving Pilot Design in Massive MIMO Networks
In this paper, we propose an active attacking strategy on a massive
multiple-input multiple-output (MIMO) network, where the pilot sequences are
obtained using the user load-achieving pilot sequence design. The user
load-achieving design ensures that the signal-to-interference-plus-noise ratio
(SINR) requirements of all the users in the massive MIMO networks are
guaranteed even in the presence of pilot contamination. However, this design
has some vulnerabilities, such as one known pilot sequence and the correlation
among the pilot sequences, that may be exploited by active attackers. In this
work, we first identify the potential vulnerabilities in the user
load-achieving pilot sequence design and then, accordingly, develop an active
attacking strategy on the network. In the proposed attacking strategy, the
active attackers transmit known pilot sequences in the uplink training and
artificial noise in the downlink data transmission. Our examination
demonstrates that the per-cell user load region is significantly reduced by the
proposed attacking strategy. As a result of the reduced per-cell user load
region, the SINR requirements of all the users are no longer guaranteed in the
presence of the active attackers. Specifically, for the worst affected users
the SINR requirements may not be ensured even with infinite antennas at the
base station.Comment: Accepted in IEEE GlobeCOM 201
Machine Learning and Location Verification in Vehicular Networks
Location information will play a very important role in emerging wireless
networks such as Intelligent Transportation Systems, 5G, and the Internet of
Things. However, wrong location information can result in poor network
outcomes. It is therefore critical to verify all location information before
further utilization in any network operation. In recent years, a number of
information-theoretic Location Verification Systems (LVSs) have been formulated
in attempts to optimally verify the location information supplied by network
users. Such LVSs, however, are somewhat limited since they rely on knowledge of
a number of channel parameters for their operation. To overcome such
limitations, in this work we introduce a Machine Learning based LVS (ML-LVS).
This new form of LVS can adapt itself to changing environments without knowing
the channel parameters. Here, for the first time, we use real-world data to
show how our ML-LVS can outperform information-theoretic LVSs. We demonstrate
this improved performance within the context of vehicular networks using
Received Signal Strength (RSS) measurements at multiple verifying base
stations. We also demonstrate the validity of the ML-LVS even in scenarios
where a sophisticated adversary optimizes her attack location.Comment: 5 pages, 3 figure
Covert Communication in Fading Channels under Channel Uncertainty
A covert communication system under block fading channels is considered where
users experience uncertainty about their channel knowledge. The transmitter
seeks to hide the covert communication to a private user by exploiting a
legitimate public communication link while the warden tries to detect this
covert communication by using a radiometer. We derive the exact expression for
the radiometers optimal threshold which determines the performance limit of the
wardens detector. Furthermore for given transmission outage constraints the
achievable rates for legitimate and covert users are analyzed while maintaining
a specific level of covertness. Our numerical results illustrate how the
achievable performance is affected by the channel uncertainty and required
level of covertness.Comment: to appear in IEEE VTC2017-Sprin
On Channel Reciprocity to Activate Uplink Channel Training for Downlink Wireless Transmission in Tactile Internet Applications
We determine, for the first time, the requirement on channel reciprocity to
activate uplink channel training, instead of downlink channel training, to
achieve a higher data rate for the downlink transmission from a multi-antenna
base station to a single-antenna user. We first derive novel closed-form
expressions for the lower bounds on the data rates achieved by the two channel
training strategies by considering the impact of finite blocklength. The
performance comparison result of these two strategies is determined by the
amount of channel reciprocity that is utilized in the uplink channel training.
We then derive an approximated expression for the minimum channel reciprocity
that enables the uplink channel training to outperform the downlink channel
training. Through numerical results, we demonstrate that this minimum channel
reciprocity decreases as the blocklength decreases or the number of transmit
antennas increases, which shows the necessity and benefits of activating the
uplink channel training for short-packet communications with multiple transmit
antennas. This work provides pivotal and unprecedented guidelines on choosing
channel training strategies and channel reciprocity calibrations, offering
valuable insights into latency reduction in the Tactile Internet applications.Comment: 6 pages, 3 figures, Submitted to IEEE ICC 2018 Worksho
Covert Wireless Communication with a Poisson Field of Interferers
In this paper, we study covert communication in wireless networks consisting
of a transmitter, Alice, an intended receiver, Bob, a warden, Willie, and a
Poisson field of interferers. Bob and Willie are subject to uncertain shot
noise due to the ambient signals from interferers in the network. With the aid
of stochastic geometry, we analyze the throughput of the covert communication
between Alice and Bob subject to given requirements on the covertness against
Willie and the reliability of decoding at Bob. We consider non-fading and
fading channels. We analytically obtain interesting findings on the impacts of
the density and the transmit power of the concurrent interferers on the covert
throughput. That is, the density and the transmit power of the interferers have
no impact on the covert throughput as long as the network stays in the
interference-limited regime, for both the non-fading and the fading cases. When
the interference is sufficiently small and comparable with the receiver noise,
the covert throughput increases as the density or the transmit power of the
concurrent interferers increases
- …