3 research outputs found
Wireless Surveillance of Two-Hop Communications
Wireless surveillance is becoming increasingly important to protect the
public security by legitimately eavesdropping suspicious wireless
communications. This paper studies the wireless surveillance of a two-hop
suspicious communication link by a half-duplex legitimate monitor. By exploring
the suspicious link's two-hop nature, the monitor can adaptively choose among
the following three eavesdropping modes to improve the eavesdropping
performance: (I) \emph{passive eavesdropping} to intercept both hops to decode
the message collectively, (II) \emph{proactive eavesdropping} via {\emph{noise
jamming}} over the first hop, and (III) \emph{proactive eavesdropping} via
{\emph{hybrid jamming}} over the second hop. In both proactive eavesdropping
modes, the (noise/hybrid) jamming over one hop is for the purpose of reducing
the end-to-end communication rate of the suspicious link and accordingly making
the interception more easily over the other hop. Under this setup, we maximize
the eavesdropping rate at the monitor by jointly optimizing the eavesdropping
mode selection as well as the transmit power for noise and hybrid jamming.
Numerical results show that the eavesdropping mode selection significantly
improves the eavesdropping rate as compared to each individual eavesdropping
mode.Comment: Submitted for conference publicatio
Proactive Eavesdropping via Jamming over HARQ-Based Communications
This paper studies the wireless surveillance of a hybrid automatic repeat
request (HARQ) based suspicious communication link over Rayleigh fading
channels. We propose a proactive eavesdropping approach, where a half-duplex
monitor can opportunistically jam the suspicious link to exploit its potential
retransmissions for overhearing more efficiently. In particular, we consider
that the suspicious link uses at most two HARQ rounds for transmitting the same
data packet, and we focus on two cases without and with HARQ combining at the
monitor receiver. In both cases, we aim to maximize the successful
eavesdropping probability at the monitor, by adaptively allocating the jamming
power in the first HARQ round according to fading channel conditions, subject
to an average jamming power constraint. For both cases, we show that the
optimal jamming power allocation follows a threshold-based policy, and the
monitor jams with constant power when the eavesdropping channel gain is less
than the threshold. Numerical results show that the proposed proactive
eavesdropping scheme achieves higher successful eavesdropping probability than
the conventional passive eavesdropping, and HARQ combining can help further
improve the eavesdropping performance.Comment: To appear in IEEE Globecom 201
Jamming-assisted Proactive Eavesdropping over Two Suspicious Communication Links
This paper studies a new and challenging wireless surveillance problem where
a legitimate monitor attempts to eavesdrop two suspicious communication links
simultaneously. To facilitate concurrent eavesdropping, our multi-antenna
legitimate monitor employs a proactive eavesdropping via jamming approach, by
selectively jamming suspicious receivers to lower the transmission rates of the
target links. In particular, we are interested in characterizing the achievable
eavesdropping rate region for the minimum-mean-squared-error (MMSE) receiver
case, by optimizing the legitimate monitor's jamming transmit covariance matrix
subject to its power budget. As the monitor cannot hear more than what
suspicious links transmit, the achievable eavesdropping rate region is
essentially the intersection of the achievable rate region for the two
suspicious links and that for the two eavesdropping links. The former region
can be purposely altered by the monitor's jamming transmit covariance matrix,
whereas the latter region is fixed when the MMSE receiver is employed.
Therefore, we first analytically characterize the achievable rate region for
the two suspicious links via optimizing the jamming transmit covariance matrix
and then obtain the achievable eavesdropping rate region for the MMSE receiver
case. Furthermore, we also extend our study to the MMSE with successive
interference cancellation (MMSE-SIC) receiver case and characterize the
corresponding achievable eavesdropping rate region by jointly optimizing the
time-sharing factor between different decoding orders. Finally, numerical
results are provided to corroborate our analysis and examine the eavesdropping
performance