3,685 research outputs found
A Survey on Device-to-Device Communication in Cellular Networks
Device-to-Device (D2D) communication was initially proposed in cellular
networks as a new paradigm to enhance network performance. The emergence of new
applications such as content distribution and location-aware advertisement
introduced new use-cases for D2D communications in cellular networks. The
initial studies showed that D2D communication has advantages such as increased
spectral efficiency and reduced communication delay. However, this
communication mode introduces complications in terms of interference control
overhead and protocols that are still open research problems. The feasibility
of D2D communications in LTE-A is being studied by academia, industry, and the
standardization bodies. To date, there are more than 100 papers available on
D2D communications in cellular networks and, there is no survey on this field.
In this article, we provide a taxonomy based on the D2D communicating spectrum
and review the available literature extensively under the proposed taxonomy.
Moreover, we provide new insights to the over-explored and under-explored areas
which lead us to identify open research problems of D2D communication in
cellular networks.Comment: 18 pages; 8 figures; Accepted for publication in IEEE Communications
Surveys and Tutorial
Scheduling in Instantaneous-Interference-Limited CR Networks with Delay Guarantees
We study an uplink multi secondary user (SU) cognitive radio system having
average delay constraints as well as an instantaneous interference constraint
to the primary user (PU). If the interference channels from the SUs to the PU
have independent but not identically distributed fading coefficients, then the
SUs will experience heterogeneous delay performances. This is because SUs
causing low interference to the PU will be scheduled more frequently, and/or
allocated more transmission power than those causing high interference. We
propose a dynamic scheduling-and-power-control algorithm that can provide the
required average delay guarantees to all SUs as well as protecting the PU from
interference. Using the Lyapunov technique, we show that our algorithm is
asymptotically delay optimal while satisfying the delay and interference
constraints. We support our findings by extensive system simulations and show
the robustness of the proposed algorithm against channel estimation errors.Comment: arXiv admin note: substantial text overlap with arXiv:1410.746
Optimal Slotted ALOHA under Delivery Deadline Constraint for Multiple-Packet Reception
This paper considers the slotted ALOHA protocol in a communication channel
shared by N users. It is assumed that the channel has the multiple-packet
reception (MPR) capability that allows the correct reception of up to M () time-overlapping packets. To evaluate the reliability in the
scenario that a packet needs to be transmitted within a strict delivery
deadline D () (in unit of slot) since its arrival at the head of
queue, we consider the successful delivery probability (SDP) of a packet as
performance metric of interest. We derive the optimal transmission probability
that maximizes the SDP for any and any , and show it
can be computed by a fixed-point iteration. In particular, the case for D = 1
(i.e., throughput maximization) is first completely addressed in this paper.
Based on these theoretical results, for real-life scenarios where N may be
unknown and changing, we develop a distributed algorithm that enables each user
to tune its transmission probability at runtime according to the estimate of N.
Simulation results show that the proposed algorithm is effective in dynamic
scenarios, with near-optimal performance
On Green Energy Powered Cognitive Radio Networks
Green energy powered cognitive radio (CR) network is capable of liberating
the wireless access networks from spectral and energy constraints. The
limitation of the spectrum is alleviated by exploiting cognitive networking in
which wireless nodes sense and utilize the spare spectrum for data
communications, while dependence on the traditional unsustainable energy is
assuaged by adopting energy harvesting (EH) through which green energy can be
harnessed to power wireless networks. Green energy powered CR increases the
network availability and thus extends emerging network applications. Designing
green CR networks is challenging. It requires not only the optimization of
dynamic spectrum access but also the optimal utilization of green energy. This
paper surveys the energy efficient cognitive radio techniques and the
optimization of green energy powered wireless networks. Existing works on
energy aware spectrum sensing, management, and sharing are investigated in
detail. The state of the art of the energy efficient CR based wireless access
network is discussed in various aspects such as relay and cooperative radio and
small cells. Envisioning green energy as an important energy resource in the
future, network performance highly depends on the dynamics of the available
spectrum and green energy. As compared with the traditional energy source, the
arrival rate of green energy, which highly depends on the environment of the
energy harvesters, is rather random and intermittent. To optimize and adapt the
usage of green energy according to the opportunistic spectrum availability, we
discuss research challenges in designing cognitive radio networks which are
powered by energy harvesters
A Non-Stationary Bandit-Learning Approach to Energy-Efficient Femto-Caching with Rateless-Coded Transmission
The ever-increasing demand for media streaming together with limited backhaul
capacity renders developing efficient file-delivery methods imperative. One
such method is femto-caching, which, despite its great potential, imposes
several challenges such as efficient resource management. We study a resource
allocation problem for joint caching and transmission in small cell networks,
where the system operates in two consecutive phases: (i) cache placement, and
(ii) joint file- and transmit power selection followed by broadcasting. We
define the utility of every small base station in terms of the number of
successful reconstructions per unit of transmission power. We then formulate
the problem as to select a file from the cache together with a transmission
power level for every broadcast round so that the accumulated utility over the
horizon is maximized. The former problem boils down to a stochastic knapsack
problem, and we cast the latter as a multi-armed bandit problem. We develop a
solution to each problem and provide theoretical and numerical evaluations. In
contrast to the state-of-the-art research, the proposed approach is especially
suitable for networks with time-variant statistical properties. Moreover, it is
applicable and operates well even when no initial information about the
statistical characteristics of the random parameters such as file popularity
and channel quality is available
On the Coexistence of a Primary User with an Energy Harvesting Secondary User: A Case of Cognitive Cooperation
In this paper, we consider a cognitive scenario where an energy harvesting
secondary user (SU) shares the spectrum with a primary user (PU). The secondary
source helps the primary source in delivering its undelivered packets during
periods of silence of the primary source. The primary source has a queue for
storing its data packets, whereas the secondary source has two data queues; a
queue for storing its own packets and the other for storing the fraction of the
undelivered primary packets accepted for relaying. The secondary source is
assumed to be a battery-based node which harvests energy packets from the
environment. In addition to its data queues, the SU has an energy queue to
store the harvested energy packets. The secondary energy packets are used for
primary packets decoding and data packets transmission. More specifically, if
the secondary energy queue is empty, the secondary source can neither help the
primary source nor transmit a packet from the data queues. The energy queue is
modeled as a discrete time queue with Markov arrival and service processes. Due
to the interaction of the queues, we provide inner and outer bounds on the
stability region of the proposed system. We investigate the impact of the
energy arrival rate on the stability region. Numerical results show the
significant gain of cooperation.Comment: Accepted for publication in Wireless Communications & Mobile
Computing (WCMC
Power Allocation and Transmitter Switching for Broadcasting with Multiple Energy Harvesting Transmitters
With the advancement of battery technology, energy harvesting communication
systems attracted great research attention in recent years. However, energy
harvesting communication systems with multiple transmitters and multiple
receivers have not been considered yet. In this paper, the problem of
broadcasting in a communication system with multiple energy harvesting
transmitters and multiple receivers is studied. First, regarding the
transmitters as a 'hole transmitter' [1], the optimal total transmission power
is obtained and the optimal power allocation policy in [2] is extended to our
system setup, with the aim of minimizing the transmission completion time.
Then, a simpler power allocation policy is developed to allocate the optimal
total transmission power to the data transmissions. As transmitter switching
can provide flexibility and robustness to an energy harvesting communication
system, especially when a transmitter is broken or the energy harvested by a
transmitter is insufficient, a transmitter switching policy is further
developed to choose a suitable transmitter to work whenever necessary. The
results show that the proposed power allocation policy performs close to the
optimal one and outperforms some heuristic ones in terms of transmission
completion time. Besides, the proposed transmitter switching policy outperforms
some heuristic ones in terms of number of switches
A Game Theory Interpretation for Multiple Access in Cognitive Radio Networks with Random Number of Secondary Users
In this paper a new multiple access algorithm for cognitive radio networks
based on game theory is presented. We address the problem of a multiple access
system where the number of users and their types are unknown. In order to do
this, the framework is modelled as a non-cooperative Poisson game in which all
the players are unaware of the total number of devices participating
(population uncertainty). We propose a scheme where failed attempts to transmit
(collisions) are penalized. In terms of this, we calculate the optimum
penalization in mixed strategies. The proposed scheme conveys to a Nash
equilibrium where a maximum in the possible throughput is achieved.Comment: 12 pages, 11 figures. Submitted for possible publication in IEEE
Journal in Communication
Power-Efficient Resource Allocation in C-RANs with SINR Constraints and Deadlines
In this paper, we address the problem of power-efficient resource management
in Cloud Radio Access Networks (C-RANs).
Specifically, we consider the case where Remote Radio Heads (RRHs) perform
data transmission, and signal processing is executed in a virtually centralized
Base-Band Units (BBUs) pool. Users request to transmit at different time
instants; they demand minimum signal-to-noise-plus-interference ratio (SINR)
guarantees, and their requests must be accommodated within a given deadline.
These constraints pose significant challenges to the management of C-RANs and,
as we will show, considerably impact the allocation of processing and radio
resources in the network.
Accordingly, we analyze the power consumption of the C-RAN system, and we
formulate the power consumption minimization problem as a weighted joint
scheduling of processing and power allocation problem for C-RANs with minimum
SINR and finite horizon constraints.
The problem is a Mixed Integer Non-Linear Program (MINLP), and we propose an
optimal offline solution based on Dynamic Programming (DP).
We show that the optimal solution is of exponential complexity, thus we
propose a sub-optimal greedy online algorithm of polynomial complexity.
We assess the performance of the two proposed solutions through extensive
numerical results.
Our solution aims to reach an appropriate trade-off between minimizing the
power consumption and maximizing the percentage of satisfied users.
We show that it results in power consumption that is only marginally higher
than the optimum, at significantly lower complexity
Information Freshness and Packet Drop Rate Interplay in a Two-User Multi-Access Channel
In this work, we combine the two notions of timely delivery of information in
order to study their interplay; namely, deadline-constrained packet delivery
due to latency constraints and freshness of information at the destination.
More specifically, we consider a two-user multiple access setup with random
access, in which user 1 is a wireless device with a queue and has external
bursty traffic which is deadline-constrained, while user 2 monitors a sensor
and transmits status updates to the destination. For this simple, yet
meaningful setup, we provide analytical expressions for the throughput and drop
probability of user 1, and an analytical expression for the average Age of
Information (AoI) of user 2 monitoring the sensor. The relations reveal that
there is a trade-off between the average AoI of user 2 and the drop rate of
user 1: the lower the average AoI, the higher the drop rate, and vice versa.
Simulations corroborate the validity of our theoretical results.Comment: Submitted to GLOBECO
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