288 research outputs found
Adaptive Mode Selection and Power Allocation in Bidirectional Buffer-aided Relay Networks
In this paper, we consider the problem of sum rate maximization in a
bidirectional relay network with fading. Hereby, user 1 and user 2 communicate
with each other only through a relay, i.e., a direct link between user 1 and
user 2 is not present. In this network, there exist six possible transmission
modes: four point-to-point modes (user 1-to-relay, user 2-to-relay,
relay-to-user 1, relay-to-user 2), a multiple access mode (both users to the
relay), and a broadcast mode (the relay to both users). Most existing protocols
assume a fixed schedule of using a subset of the aforementioned transmission
modes, as a result, the sum rate is limited by the capacity of the weakest link
associated with the relay in each time slot. Motivated by this limitation, we
develop a protocol which is not restricted to adhere to a predefined schedule
for using the transmission modes. Therefore, all transmission modes of the
bidirectional relay network can be used adaptively based on the instantaneous
channel state information (CSI) of the involved links. To this end, the relay
has to be equipped with two buffers for the storage of the information received
from users 1 and 2, respectively. For the considered network, given a total
average power budget for all nodes, we jointly optimize the transmission mode
selection and power allocation based on the instantaneous CSI in each time slot
for sum rate maximization. Simulation results show that the proposed protocol
outperforms existing protocols for all signal-to-noise ratios (SNRs).
Specifically, we obtain a considerable gain at low SNRs due to the adaptive
power allocation and at high SNRs due to the adaptive mode selection.Comment: arXiv admin note: substantial text overlap with arXiv:1303.373
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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