22 research outputs found
On Strong Secrecy for Multiple Access Channel with States and Causal CSI
Strong secrecy communication over a discrete memoryless state-dependent
multiple access channel (SD-MAC) with an external eavesdropper is investigated.
The channel is governed by discrete memoryless and i.i.d. channel states and
the channel state information (CSI) is revealed to the encoders in a causal
manner. An inner bound of the capacity is provided. To establish the inner
bound, we investigate coding schemes incorporating wiretap coding and secret
key agreement between the sender and the legitimate receiver. Two kinds of
block Markov coding schemes are studied. The first one uses backward decoding
and Wyner-Ziv coding and the secret key is constructed from a lossy
reproduction of the CSI. The other one is an extended version of the existing
coding scheme for point-to-point wiretap channels with causal CSI. We further
investigate some capacity-achieving cases for state-dependent multiple access
wiretap channels (SD-MAWCs) with degraded message sets. It turns out that the
two coding schemes are both optimal in these cases.Comment: Accepted for presentation at ISIT202
Modulation and Estimation with a Helper
The problem of transmitting a parameter value over an additive white Gaussian
noise (AWGN) channel is considered, where, in addition to the transmitter and
the receiver, there is a helper that observes the noise non-causally and
provides a description of limited rate to the transmitter and/or
the receiver. We derive upper and lower bounds on the optimal achievable
-th moment of the estimation error and show that they coincide for
small values of and for low SNR values. The upper bound relies on a
recently proposed channel-coding scheme that effectively conveys
bits essentially error-free and the rest of the rate - over the same AWGN
channel without help, with the error-free bits allocated to the most
significant bits of the quantized parameter. We then concentrate on the setting
with a total transmit energy constraint, for which we derive achievability
results for both channel coding and parameter modulation for several scenarios:
when the helper assists only the transmitter or only the receiver and knows the
noise, and when the helper assists the transmitter and/or the receiver and
knows both the noise and the message. In particular, for the message-informed
helper that assists both the receiver and the transmitter, it is shown that the
error probability in the channel-coding task decays doubly exponentially.
Finally, we translate these results to those for continuous-time power-limited
AWGN channels with unconstrained bandwidth. As a byproduct, we show that the
capacity with a message-informed helper that is available only at the
transmitter can exceed the capacity of the same scenario when the helper knows
only the noise but not the message.Comment: This work has been submitted to the IEEE for possible publication.
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