97,880 research outputs found
Cooperative Binning for Semi-deterministic Channels with Non-causal State Information
The capacity of the semi-deterministic relay channel (SD-RC) with non-causal
channel state information (CSI) only at the encoder and decoder is
characterized. The capacity is achieved by a scheme based on
cooperative-bin-forward. This scheme allows cooperation between the transmitter
and the relay without the need to decode a part of the message by the relay.
The transmission is divided into blocks and each deterministic output of the
channel (observed by the relay) is mapped to a bin. The bin index is used by
the encoder and the relay to choose the cooperation codeword in the next
transmission block. In causal settings the cooperation is independent of the
state. In \emph{non-causal} settings dependency between the relay's
transmission and the state can increase the transmission rates. The encoder
implicitly conveys partial state information to the relay. In particular, it
uses the states of the next block and selects a cooperation codeword
accordingly and the relay transmission depends on the cooperation codeword and
therefore also on the states. We also consider the multiple access channel with
partial cribbing as a semi-deterministic channel. The capacity region of this
channel with non-causal CSI is achieved by the new scheme. Examining the result
in several cases, we introduce a new problem of a point-to-point (PTP) channel
where the state is provided to the transmitter by a state encoder.
Interestingly, even though the CSI is also available at the receiver, we
provide an example which shows that the capacity with non-causal CSI at the
state encoder is strictly larger than the capacity with causal CSI
Information Theoretic Limits of State-dependent Networks
We investigate the information theoretic limits of two types of state-dependent models in this dissertation. These models capture a wide range of wireless communication scenarios where there are interference cognition among transmitters. Hence, information theoretic studies of these models provide useful guidelines for designing new interference cancellation schemes in practical wireless networks.
In particular, we first study the two-user state-dependent Gaussian multiple access channel (MAC) with a helper. The channel is corrupted by an additive Gaussian state sequence known to neither the transmitters nor the receiver, but to a helper noncausally, which assists state cancellation at the receiver. Inner and outer bounds on the capacity region are first derived, which improve the state-of-the-art bounds given in the literature. Further comparison of these bounds yields either segments on the capacity region boundary or the full capacity region by considering various regimes of channel parameters.
We then study the two-user Gaussian state-dependent Z-interference channel (Z-IC), in which two receivers are corrupted respectively by two correlated states that are noncausally known to transmitters, but unknown to receivers. Three interference regimes are studied, and the capacity region or the sum capacity boundary is characterized either fully or partially under various channel parameters. The impact of the correlation between the states on the cancellation of state and interference as well as the achievability of the capacity is demonstrated via numerical analysis.
Finally, we extend our results on the state-dependent Z-IC to the state-dependent regular IC. As both receivers in the regular IC are interfered, more sophisticated achievable schemes are designed. For the very strong regime, the capacity region is achieved by a scheme where the two transmitters implement a cooperative dirty paper coding. For the strong but not very strong regime, the sum-rate capacity is characterized by rate splitting, layered dirty paper coding and successive cancellation. For the weak regime, the sum-rate capacity is achieved via dirty paper coding individually at two receivers as well as treating interference as noise. Numerical investigation indicates that for the regular IC, the correlation between states impacts the achievability of the channel capacity in a different way from that of the Z-IC
Fundamental Limits of Multiple-Access Integrated Sensing and Communication Systems
A memoryless state-dependent multiple access channel is considered to model
an integrated sensing and communication system, where two transmitters wish to
convey messages to a receiver while simultaneously estimating the sensing state
sequences through echo signals. In particular, the sensing states are assumed
to be correlated with the channel state, and the receiver has imperfect channel
state information. In this setup, improved inner and outer bounds for
capacity-distortion region are derived. The inner bound is based on an
achievable scheme that combines message cooperation and joint compression via
distributed Wyner-Ziv coding at each transmitter, resulting in unified
cooperative communication and sensing. The outer bound is based on the ideas of
dependence balance for communication rate and rate-limited constraints on
sensing distortion. The proposed inner and outer bounds are proved to improve
the state-of-the-art bounds. Finally, numerical examples are provided to
demonstrate that our new inner and outer bounds strictly improve the existing
results
On Cooperative Multiple Access Channels with Delayed CSI at Transmitters
We consider a cooperative two-user multiaccess channel in which the
transmission is controlled by a random state. Both encoders transmit a common
message and, one of the encoders also transmits an individual message. We study
the capacity region of this communication model for different degrees of
availability of the states at the encoders, causally or strictly causally. In
the case in which the states are revealed causally to both encoders but not to
the decoder we find an explicit characterization of the capacity region in the
discrete memoryless case. In the case in which the states are revealed only
strictly causally to both encoders, we establish inner and outer bounds on the
capacity region. The outer bound is non-trivial, and has a relatively simple
form. It has the advantage of incorporating only one auxiliary random variable.
We then introduce a class of cooperative multiaccess channels with states known
strictly causally at both encoders for which the inner and outer bounds agree;
and so we characterize the capacity region for this class. In this class of
channels, the state can be obtained as a deterministic function of the channel
inputs and output. We also study the model in which the states are revealed,
strictly causally, in an asymmetric manner, to only one encoder. Throughout the
paper, we discuss a number of examples; and compute the capacity region of some
of these examples. The results shed more light on the utility of delayed
channel state information for increasing the capacity region of state-dependent
cooperative multiaccess channels; and tie with recent progress in this
framework.Comment: 54 pages. To appear in IEEE Transactions on Information Theory. arXiv
admin note: substantial text overlap with arXiv:1201.327
Principles of Physical Layer Security in Multiuser Wireless Networks: A Survey
This paper provides a comprehensive review of the domain of physical layer
security in multiuser wireless networks. The essential premise of
physical-layer security is to enable the exchange of confidential messages over
a wireless medium in the presence of unauthorized eavesdroppers without relying
on higher-layer encryption. This can be achieved primarily in two ways: without
the need for a secret key by intelligently designing transmit coding
strategies, or by exploiting the wireless communication medium to develop
secret keys over public channels. The survey begins with an overview of the
foundations dating back to the pioneering work of Shannon and Wyner on
information-theoretic security. We then describe the evolution of secure
transmission strategies from point-to-point channels to multiple-antenna
systems, followed by generalizations to multiuser broadcast, multiple-access,
interference, and relay networks. Secret-key generation and establishment
protocols based on physical layer mechanisms are subsequently covered.
Approaches for secrecy based on channel coding design are then examined, along
with a description of inter-disciplinary approaches based on game theory and
stochastic geometry. The associated problem of physical-layer message
authentication is also introduced briefly. The survey concludes with
observations on potential research directions in this area.Comment: 23 pages, 10 figures, 303 refs. arXiv admin note: text overlap with
arXiv:1303.1609 by other authors. IEEE Communications Surveys and Tutorials,
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