7,853 research outputs found
Secure Communications for the Two-user Broadcast Channel with Random Traffic
In this work, we study the stability region of the two-user broadcast channel
(BC) with bursty data arrivals and security constraints. We consider the
scenario, where one of the receivers has a secrecy constraint and its packets
need to be kept secret from the other receiver. This is achieved by employing
full-duplexing at the receiver with the secrecy constraint, so that it
transmits a jamming signal to impede the reception of the other receiver. In
this context, the stability region of the two-user BC is characterized for the
general decoding case. Then, assuming two different decoding schemes the
respective stability regions are derived. The effect of self-interference due
to the full-duplex operation on the stability region is also investigated. The
stability region of the BC with a secrecy constraint, where the receivers do
not have full duplex capability can be obtained as a special case of the
results derived in this paper. In addition, the paper considers the problem of
maximizing the saturated throughput of the queue, whose packets does not
require to be kept secret under minimum service guarantees for the other queue.
The results provide new insights on the effect of the secrecy constraint on the
stability region of the BC. In particular, it is shown that the stability
region with secrecy constraint is sensitive to the coefficient of
self-interference cancelation under certain cases.Comment: Submitted for journal publicatio
On Physically Secure and Stable Slotted ALOHA System
In this paper, we consider the standard discrete-time slotted ALOHA with a
finite number of terminals with infinite size buffers. In our study, we jointly
consider the stability of this system together with the physical layer
security. We conduct our studies on both dominant and original systems, where
in a dominant system each terminal always has a packet in its buffer unlike in
the original system. For N = 2, we obtain the secrecy-stability regions for
both dominant and original systems. Furthermore, we obtain the transmission
probabilities, which optimize system throughput. Lastly, this paper proposes a
new methodology in terms of obtaining the joint stability and secrecy regions.Comment: 7 Pages, 8 Figures, Allerton 200
Random Access in DVB-RCS2: Design and Dynamic Control for Congestion Avoidance
In the current DVB generation, satellite terminals are expected to be
interactive and capable of transmission in the return channel with satisfying
quality. Considering the bursty nature of their traffic and the long
propagation delay, the use of a random access technique is a viable solution
for such a Medium Access Control (MAC) scenario. In this paper, random access
communication design in DVB-RCS2 is considered with particular regard to the
recently introduced Contention Resolution Diversity Slotted Aloha (CRDSA)
technique. This paper presents a model for design and tackles some issues on
performance evaluation of the system by giving intuitive and effective tools.
Moreover, dynamic control procedures that are able to avoid congestion at the
gateway are introduced. Results show the advantages brought by CRDSA to
DVB-RCS2 with regard to the previous state of the art.Comment: Accepted for publication: IEEE Transactions on Broadcasting; IEEE
Transactions on Broadcasting, 201
Joint Scheduling and ARQ for MU-MIMO Downlink in the Presence of Inter-Cell Interference
User scheduling and multiuser multi-antenna (MU-MIMO) transmission are at the
core of high rate data-oriented downlink schemes of the next-generation of
cellular systems (e.g., LTE-Advanced). Scheduling selects groups of users
according to their channels vector directions and SINR levels. However, when
scheduling is applied independently in each cell, the inter-cell interference
(ICI) power at each user receiver is not known in advance since it changes at
each new scheduling slot depending on the scheduling decisions of all
interfering base stations. In order to cope with this uncertainty, we consider
the joint operation of scheduling, MU-MIMO beamforming and Automatic Repeat
reQuest (ARQ). We develop a game-theoretic framework for this problem and build
on stochastic optimization techniques in order to find optimal scheduling and
ARQ schemes. Particularizing our framework to the case of "outage service
rates", we obtain a scheme based on adaptive variable-rate coding at the
physical layer, combined with ARQ at the Logical Link Control (ARQ-LLC). Then,
we present a novel scheme based on incremental redundancy Hybrid ARQ (HARQ)
that is able to achieve a throughput performance arbitrarily close to the
"genie-aided service rates", with no need for a genie that provides
non-causally the ICI power levels. The novel HARQ scheme is both easier to
implement and superior in performance with respect to the conventional
combination of adaptive variable-rate coding and ARQ-LLC.Comment: Submitted to IEEE Transactions on Communications, v2: small
correction
On the Stability of Contention Resolution Diversity Slotted ALOHA
In this paper a Time Division Multiple Access (TDMA) based Random Access (RA)
channel with Successive Interference Cancellation (SIC) is considered for a
finite user population and reliable retransmission mechanism on the basis of
Contention Resolution Diversity Slotted ALOHA (CRDSA). A general mathematical
model based on Markov Chains is derived which makes it possible to predict the
stability regions of SIC-RA channels, the expected delays in equilibrium and
the selection of parameters for a stable channel configuration. Furthermore the
model enables the estimation of the average time before reaching instability.
The presented model is verified against simulations and numerical results are
provided for comparison of the stability of CRDSA versus the stability of
traditional Slotted ALOHA (SA). The presented results show that CRDSA has not
only a high gain over SA in terms of throughput but also in its stability.Comment: 10 pages, 12 figures This paper is submitted to the IEEE Transactions
on Communications for possible publication. The IEEE copyright notice applie
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