809 research outputs found
Cost-optimal caching for D2D networks with user mobility: Modeling, analysis, and computational approaches
Caching popular files at user equipments (UEs) provides an effective way to
alleviate the burden of the backhaul networks. Generally, popularity-based
caching is not a system-wide optimal strategy, especially for user mobility
scenarios. Motivated by this observation, we consider optimal caching with
presence of mobility. A cost-optimal caching problem (COCP) for
device-to-device (D2D) networks is modelled, in which the impact of user
mobility, cache size, and total number of encoded segments are all accounted
for. Compared with the related studies, our investigation guarantees that the
collected segments are non-overlapping, takes into account the cost of
downloading from the network, and provides a rigorous problem complexity
analysis. The hardness of the problem is proved via a reduction from the
satisfiability problem. Next, a lower-bounding function of the objective
function is derived. By the function, an approximation of COCP (ACOCP)
achieving linearization is obtained, which features two advantages. First, the
ACOCP approach can use an off-the-shelf integer linear programming algorithm to
obtain the global optimal solution, and it can effectively deliver solutions
for small-scale and mediumscale system scenarios. Second, and more importantly,
based on the ACOCP approach, one can derive the lower bound of global optimum
of COCP, thus enabling performance benchmarking of any suboptimal algorithm. To
tackle large scenarios with low complexity, we first prove that the optimal
caching placement of one user, giving other users' caching placements, can be
derived in polynomial time. Then, based on this proof, a mobility aware
user-by-user (MAUU) algorithm is developed. Simulation results verify the
effectivenesses of the two approaches by comparing them to the lower bound of
global optimum and conventional caching algorithms
Generalized Sparse and Low-Rank Optimization for Ultra-Dense Networks
Ultra-dense network (UDN) is a promising technology to further evolve
wireless networks and meet the diverse performance requirements of 5G networks.
With abundant access points, each with communication, computation and storage
resources, UDN brings unprecedented benefits, including significant improvement
in network spectral efficiency and energy efficiency, greatly reduced latency
to enable novel mobile applications, and the capability of providing massive
access for Internet of Things (IoT) devices. However, such great promises come
with formidable research challenges. To design and operate such complex
networks with various types of resources, efficient and innovative
methodologies will be needed. This motivates the recent introduction of highly
structured and generalizable models for network optimization. In this article,
we present some recently proposed large-scale sparse and low-rank frameworks
for optimizing UDNs, supported by various motivating applications. A special
attention is paid on algorithmic approaches to deal with nonconvex objective
functions and constraints, as well as computational scalability.Comment: This paper has been accepted by IEEE Communication Magazine, Special
Issue on Heterogeneous Ultra Dense Network
Five Disruptive Technology Directions for 5G
New research directions will lead to fundamental changes in the design of
future 5th generation (5G) cellular networks. This paper describes five
technologies that could lead to both architectural and component disruptive
design changes: device-centric architectures, millimeter Wave, Massive-MIMO,
smarter devices, and native support to machine-2-machine. The key ideas for
each technology are described, along with their potential impact on 5G and the
research challenges that remain
Living in a PIT-less World: A Case Against Stateful Forwarding in Content-Centric Networking
Information-Centric Networking (ICN) is a recent paradigm that claims to
mitigate some limitations of the current IP-based Internet architecture. The
centerpiece of ICN is named and addressable content, rather than hosts or
interfaces. Content-Centric Networking (CCN) is a prominent ICN instance that
shares the fundamental architectural design with its equally popular academic
sibling Named-Data Networking (NDN). CCN eschews source addresses and creates
one-time virtual circuits for every content request (called an interest). As an
interest is forwarded it creates state in intervening routers and the requested
content back is delivered over the reverse path using that state.
Although a stateful forwarding plane might be beneficial in terms of
efficiency, and resilience to certain types of attacks, this has not been
decisively proven via realistic experiments. Since keeping per-interest state
complicates router operations and makes the infrastructure susceptible to
router state exhaustion attacks (e.g., there is currently no effective defense
against interest flooding attacks), the value of the stateful forwarding plane
in CCN should be re-examined.
In this paper, we explore supposed benefits and various problems of the
stateful forwarding plane. We then argue that its benefits are uncertain at
best and it should not be a mandatory CCN feature. To this end, we propose a
new stateless architecture for CCN that provides nearly all functionality of
the stateful design without its headaches. We analyze performance and resource
requirements of the proposed architecture, via experiments.Comment: 10 pages, 6 figure
Stochastic Design and Analysis of Wireless Cloud Caching Networks
This paper develops a stochastic geometry-based approach for the modeling,
analysis, and optimization of wireless cloud caching networks comprised of
multiple-antenna radio units (RUs) inside clouds. We consider the Matern
cluster process to model RUs and the probabilistic content placement to cache
files in RUs. Accordingly, we study the exact hit probability for a user of
interest for two strategies; closest selection, where the user is served by the
closest RU that has its requested file, and best selection, where the serving
RU having the requested file provides the maximum instantaneous received power
at the user. As key steps for the analyses, the Laplace transform of out of
cloud interference, the desired link distance distribution in the closest
selection, and the desired link received power distribution in the best
selection are derived. Also, we approximate the derived exact hit probabilities
for both the closest and the best selections in such a way that the related
objective functions for the content caching design of the network can lead to
tractable concave optimization problems. Solving the optimization problems, we
propose algorithms to efficiently find their optimal content placements.
Finally, we investigate the impact of different parameters such as the number
of antennas and the cache memory size on the caching performance
Caching at the Wireless Edge: Design Aspects, Challenges and Future Directions
Caching at the wireless edge is a promising way of boosting spectral
efficiency and reducing energy consumption of wireless systems. These
improvements are rooted in the fact that popular contents are reused,
asynchronously, by many users. In this article, we first introduce methods to
predict the popularity distributions and user preferences, and the impact of
erroneous information. We then discuss the two aspects of caching systems,
namely content placement and delivery. We expound the key differences between
wired and wireless caching, and outline the differences in the system arising
from where the caching takes place, e.g., at base stations, or on the wireless
devices themselves. Special attention is paid to the essential limitations in
wireless caching, and possible tradeoffs between spectral efficiency, energy
efficiency and cache size.Comment: Published in IEEE Communications Magazin
Echo State Networks for Proactive Caching in Cloud-Based Radio Access Networks with Mobile Users
In this paper, the problem of proactive caching is studied for cloud radio
access networks (CRANs). In the studied model, the baseband units (BBUs) can
predict the content request distribution and mobility pattern of each user,
determine which content to cache at remote radio heads and BBUs. This problem
is formulated as an optimization problem which jointly incorporates backhaul
and fronthaul loads and content caching. To solve this problem, an algorithm
that combines the machine learning framework of echo state networks with
sublinear algorithms is proposed. Using echo state networks (ESNs), the BBUs
can predict each user's content request distribution and mobility pattern while
having only limited information on the network's and user's state. In order to
predict each user's periodic mobility pattern with minimal complexity, the
memory capacity of the corresponding ESN is derived for a periodic input. This
memory capacity is shown to be able to record the maximum amount of user
information for the proposed ESN model. Then, a sublinear algorithm is proposed
to determine which content to cache while using limited content request
distribution samples. Simulation results using real data from Youku and the
Beijing University of Posts and Telecommunications show that the proposed
approach yields significant gains, in terms of sum effective capacity, that
reach up to 27.8% and 30.7%, respectively, compared to random caching with
clustering and random caching without clustering algorithm.Comment: Accepted in the IEEE Transactions on Wireless Communication
Cache-enabled Device-to-Device Communications: Offloading Gain and Energy Cost
By caching files at users, content delivery traffic can be offloaded via
device-to-device (D2D) links if a helper user is willing to transmit the cached
file to the user who requests the file. In practice, the user device has
limited battery capacity, and may terminate the D2D connection when its battery
has little energy left. Thus, taking the battery consumption allowed by the
helper users to support D2D into account introduces a reduction in the possible
amount of offloading. In this paper, we investigate the relationship between
offloading gain of the system and energy cost of each helper user. To this end,
we introduce a user-centric protocol to control the energy cost for a helper
user to transmit the file. Then, we optimize the proactive caching policy to
maximize the offloading opportunity, and optimize the transmit power at each
helper to maximize the offloading probability. Finally, we evaluate the overall
amount of traffic offloaded to D2D links and evaluate the average energy
consumption at each helper, with the optimized caching policy and transmit
power. Simulations show that a significant amount of traffic can be offloaded
even when the energy cost is kept low.Comment: A part of this work was published in IEEE WCNC 2016 with title
"Energy Costs for Traffic Offloading by Cache-enabled D2D Communications
Application of Machine Learning in Wireless Networks: Key Techniques and Open Issues
As a key technique for enabling artificial intelligence, machine learning
(ML) is capable of solving complex problems without explicit programming.
Motivated by its successful applications to many practical tasks like image
recognition, both industry and the research community have advocated the
applications of ML in wireless communication. This paper comprehensively
surveys the recent advances of the applications of ML in wireless
communication, which are classified as: resource management in the MAC layer,
networking and mobility management in the network layer, and localization in
the application layer. The applications in resource management further include
power control, spectrum management, backhaul management, cache management,
beamformer design and computation resource management, while ML based
networking focuses on the applications in clustering, base station switching
control, user association and routing. Moreover, literatures in each aspect is
organized according to the adopted ML techniques. In addition, several
conditions for applying ML to wireless communication are identified to help
readers decide whether to use ML and which kind of ML techniques to use, and
traditional approaches are also summarized together with their performance
comparison with ML based approaches, based on which the motivations of surveyed
literatures to adopt ML are clarified. Given the extensiveness of the research
area, challenges and unresolved issues are presented to facilitate future
studies, where ML based network slicing, infrastructure update to support ML
based paradigms, open data sets and platforms for researchers, theoretical
guidance for ML implementation and so on are discussed.Comment: 34 pages,8 figure
Mobile Edge Caching: An Optimal Auction Approach
With the explosive growth of wireless data, the sheer size of the mobile
traffic is challenging the capacity of current wireless systems. To tackle this
challenge, mobile edge caching has emerged as a promising paradigm recently, in
which the service providers (SPs) prefetch some popular contents in advance and
cache them locally at the network edge. When requested, those locally cached
contents can be directly delivered to users with low latency, thus alleviating
the traffic load over backhaul channels during peak hours and enhancing the
quality-of-experience (QoE) of users simultaneously. Due to the limited
available cache space, it makes sense for the SP to cache the most profitable
contents. Nevertheless, users' true valuations of contents are their private
knowledge, which is unknown to the SP in general. This information asymmetry
poses a significant challenge for effective caching at the SP side. Further,
the cached contents can be delivered with different quality, which needs to be
chosen judiciously to balance delivery costs and user satisfaction. To tackle
these difficulties, in this paper, we propose an optimal auction mechanism from
the perspective of the SP. In the auction, the SP determines the cache space
allocation over contents and user payments based on the users' (possibly
untruthful) reports of their valuations so that the SP's expected revenue is
maximized. The advocated mechanism is designed to elicit true valuations from
the users (incentive compatibility) and to incentivize user participation
(individual rationality). In addition, we devise a computationally efficient
method for calculating the optimal cache space allocation and user payments. We
further examine the optimal choice of the content delivery quality for the case
with a large number of users and derive a closed-form solution to compute the
optimal delivery quality
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