68 research outputs found
Full-Duplex Relay with Jamming Protocol for Improving Physical-Layer Security
This paper proposes a jointly cooperative relay and jamming protocol based on
full-duplex (FD) capable relay to increase the source-destination secrecy rate
in the presence of different types of eavesdroppers. In this so called
\textit{FD-Relay with jamming (FDJ)} protocol, the FD-Relay, first,
simultaneously receives data and sends jamming to the eavesdropper, and, then,
forwards the data, while the source jams the eavesdropper. Achievable secrecy
rates of the proposed FDJ in presence of different eavesdropper types and
self-interference (SI) are derived and compared with those of the traditional
half-duplex (HD) relay. The adaptive power allocation for secrecy rate
maximization in a multi-carrier scenario for both proposed FDJ and HD-Relay is
formulated as a non-convex optimization problem and corresponding iterative
solution algorithm is developed using the difference-of-two-concave-functions
(DC) programming technique. The simulation results confirm that FDJ offers
significant improvements in the secrecy rate over the HD-Relay.Comment: PIMRC 201
Joint User-Association and Resource-Allocation in Virtualized Wireless Networks
In this paper, we consider a down-link transmission of multicell virtualized
wireless networks (VWNs) where users of different service providers (slices)
within a specific region are served by a set of base stations (BSs) through
orthogonal frequency division multiple access (OFDMA). In particular, we
develop a joint BS assignment, sub-carrier and power allocation algorithm to
maximize the network throughput, while satisfying the minimum required rate of
each slice. Under the assumption that each user at each transmission instance
can connect to no more than one BS, we introduce the user-association factor
(UAF) to represent the joint sub-carrier and BS assignment as the optimization
variable vector in the mathematical problem formulation. Sub-carrier reuse is
allowed in different cells, but not within one cell. As the proposed
optimization problem is inherently non-convex and NP-hard, by applying the
successive convex approximation (SCA) and complementary geometric programming
(CGP), we develop an efficient two-step iterative approach with low
computational complexity to solve the proposed problem. For a given
power-allocation, Step 1 derives the optimum userassociation and subsequently,
for an obtained user-association, Step 2 find the optimum power-allocation.
Simulation results demonstrate that the proposed iterative algorithm
outperforms the traditional approach in which each user is assigned to the BS
with the largest average value of signal strength, and then, joint sub-carrier
and power allocation is obtained for the assigned users of each cell.
Especially, for the cell-edge users, simulation results reveal a coverage
improvement up to 57% and 71% for uniform and non-uniform users distribution,
respectively leading to more reliable transmission and higher spectrum
efficiency for VWN
Robust Spectrum Sharing via Worst Case Approach
This paper considers non-cooperative and fully-distributed power-allocation
for secondary-users (SUs) in spectrum-sharing environments when
normalized-interference to each secondary-user is uncertain. We model each
uncertain parameter by the sum of its nominal (estimated) value and a bounded
additive error in a convex set, and show that the allocated power always
converges to its equilibrium, called robust Nash equilibrium (RNE). In the case
of a bounded and symmetric uncertainty set, we show that the power allocation
problem for each SU is simplified, and can be solved in a distributed manner.
We derive the conditions for RNE's uniqueness and for convergence of the
distributed algorithm; and show that the total throughput (social utility) is
less than that at NE when RNE is unique. We also show that for multiple RNEs,
the the social utility may be higher at a RNE as compared to that at the
corresponding NE, and demonstrate that this is caused by SUs' orthogonal
utilization of bandwidth for increasing the social utility. Simulations confirm
our analysis
Completion-Time-Driven Scheduling for Uplink NOMA-Enabled Wireless Networks
Efficient scheduling policy is crucial in wireless
networks due to delay-sensitivity of many emerging applications.
In this work, we consider a joint user pairing and scheduling
(UPaS) scheme for multi-carrier non-orthogonal multiple access
(MC-NOMA)-enabled wireless networks to reduce the maximum
completion time of serving uplink users. The NOMA scheduling
problem is shown to be NP-hard and a shortest processing time
(SPT)-based strategy to solve the same problem within affordable
time and complexity is introduced. The simulation results confirm
the efficacy of the proposed scheduling scheme in terms of
the maximum completion time in comparison with orthogonal
multiple access (OMA) and random NOMA pairing
Cooperative Multi-Bitrate Video Caching and Transcoding in Multicarrier NOMA-Assisted Heterogeneous Virtualized MEC Networks
Cooperative video caching and transcoding in mobile edge computing (MEC)
networks is a new paradigm for future wireless networks, e.g., 5G and 5G
beyond, to reduce scarce and expensive backhaul resource usage by prefetching
video files within radio access networks (RANs). Integration of this technique
with other advent technologies, such as wireless network virtualization and
multicarrier non-orthogonal multiple access (MC-NOMA), provides more flexible
video delivery opportunities, which leads to enhancements both for the
network's revenue and for the end-users' service experience. In this regard, we
propose a two-phase RAF for a parallel cooperative joint multi-bitrate video
caching and transcoding in heterogeneous virtualized MEC networks. In the cache
placement phase, we propose novel proactive delivery-aware cache placement
strategies (DACPSs) by jointly allocating physical and radio resources based on
network stochastic information to exploit flexible delivery opportunities.
Then, for the delivery phase, we propose a delivery policy based on the user
requests and network channel conditions. The optimization problems
corresponding to both phases aim to maximize the total revenue of network
slices, i.e., virtual networks. Both problems are non-convex and suffer from
high-computational complexities. For each phase, we show how the problem can be
solved efficiently. We also propose a low-complexity RAF in which the
complexity of the delivery algorithm is significantly reduced. A Delivery-aware
cache refreshment strategy (DACRS) in the delivery phase is also proposed to
tackle the dynamically changes of network stochastic information. Extensive
numerical assessments demonstrate a performance improvement of up to 30% for
our proposed DACPSs and DACRS over traditional approaches.Comment: 53 pages, 24 figure
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