16 research outputs found
The three primary colors of mobile systems
In this paper, we present the notion of "mobile 3C systems in which the
"Communications", "Computing", and "Caching" (i.e., 3C) make up the three
primary resources/funcationalties, akin to the three primary colors, for a
mobile system. We argue that in future mobile networks, the roles of computing
and caching are as intrinsic and essential as communications, and only the
collective usage of these three primary resources can support the sustainable
growth of mobile systems. By defining the 3C resources in their canonical
forms, we reveal the important fact that "caching" affects the mobile system
performance by introducing non-causality into the system, whereas "computing"
achieves capacity gains by performing logical operations across mobile system
entities. Many existing capacity-enhancing techniques such as coded multicast,
collaborative transmissions, and proactive content pushing can be cast into the
native 3C framework for analytical tractability. We further illustrate the
mobile 3C concepts with practical examples, including a system on
broadcast-unicast convergence for massive media content delivery. The mobile 3C
design paradigm opens up new possibilities as well as key research problems
bearing academic and practice significance.Comment: submitted to IEEE Communications Magazine -- Feature Topic: Mobile 3C
Network
Optimal Task Scheduling in Communication-Constrained Mobile Edge Computing Systems for Wireless Virtual Reality
Mobile edge computing (MEC) is expected to be an effective solution to
deliver 360-degree virtual reality (VR) videos over wireless networks. In
contrast to previous computation-constrained MEC framework, which reduces the
computation-resource consumption at the mobile VR device by increasing the
communication-resource consumption, we develop a communications-constrained MEC
framework to reduce communication-resource consumption by increasing the
computation-resource consumption and exploiting the caching resources at the
mobile VR device in this paper. Specifically, according to the task
modularization, the MEC server can only deliver the components which have not
been stored in the VR device, and then the VR device uses the received
components and the corresponding cached components to construct the task,
resulting in low communication-resource consumption but high delay. The MEC
server can also compute the task by itself to reduce the delay, however, it
consumes more communication-resource due to the delivery of entire task.
Therefore, we then propose a task scheduling strategy to decide which
computation model should the MEC server operates, in order to minimize the
communication-resource consumption under the delay constraint. Finally, we
discuss the tradeoffs between communications, computing, and caching in the
proposed system.Comment: submitted to APCC 201
Artificial Interference Aided Physical Layer Security in Cache-enabled Heterogeneous Networks
Caching popular contents is a promising way to offload the mobile data
traffic in wireless networks, but so far the potential advantage of caching in
improving physical layer security (PLS) is rarely considered. In this paper, we
contribute to the design and theoretical understanding of exploiting the
caching ability of users to improve the PLS in a wireless heterogeneous network
(HetNet). In such network, the base station (BS) ensures the secrecy of
communication by utilizing some of the available power to transmit a pre-cached
file, such that only the eavesdropper's channel is degraded. Accordingly, the
node locations of BSs, users and eavesdroppers are first modeled as mutually
independent poisson point processes (PPPs) and the corresponding file access
protocol is developed. We then derive analytical expressions of two metrics,
average secrecy rate and secrecy coverage probability, for the proposed system.
Numerical results are provided to show the significant security advantages of
the proposed network and to characterize the impact of network resource on the
secrecy metrics.Comment: submitted to IEEE ICC 201
Delay Analysis and Optimization in Cache-enabled Multi-Cell Cooperative Networks
Caching at the base stations (BSs) has been widely adopted to reduce the
delivery delay and alleviate the backhaul traffic between BSs and the core
network. In this paper, we consider a collaborative content caching scheme
among BSs in cache-enabled multi-cell cooperative networks, where the requested
contents can be obtained from the associated BS, the other collaborative BSs or
the core network. Novelly, we model the stochastic request traffic and derive a
closed form expression for the average delay per request based on multi-class
processor sharing queuing theory. We then formulate a cooperative caching
optimization problem of minimizing the average delay under the finite cache
size constraint at BSs and show it to be at least NP-complete. Furthermore, we
prove it equivalent to the maximization of a monotone submodular function
subject to matroid constraints, allowing us to adopt the common greedy
algorithm with 1/2 performance guarantee. A heuristic greedy caching strategy
is also developed, achieving a better performance than the conventional greedy
solution. Simulation results verify the accuracy of the analytical results and
demonstrate the performance gains obtained by our proposed caching scheme.Comment: submitted to IEEE GLOBECOM 201
Treating Content Delivery in Multi-Antenna Coded Caching as General Message Sets Transmission: A DoF Region Perspective
Coded caching can create coded multicasting thus significantly accelerates
content delivery in broadcast channels with receiver caches. While the original
delivery scheme in coded caching multicasts each coded message sequentially, it
is not optimal for multiple-input multiple-output (MIMO) broadcast channels.
This work aims to investigate the full spatial multiplexing gain in
multi-antenna coded caching by transmitting all coded messages concurrently. In
specific, we propose to treat the content delivery as the transmission problem
with general message sets where all possible messages are present, each with
different length and intended for different user set. We first obtain inner and
outer bounds of the degrees of freedom (DoF) region of a -user
broadcast channel with general message sets, with and being the number
of transmit and receive antennas, respectively. Then for any given set of coded
messages, we find its minimum normalized delivery time (NDT) by searching the
optimal DoF tuple in the DoF regions. The obtained minimum NDT is optimal at
antenna configuration and is within a
multiplicative gap of to optimum at . Our
NDT results can be evaluated for any user demand with both centralized and
decentralized cache placement.Comment: Part of this work was presented at IEEE GLOBECOM 201
Bandwidth Gain from Mobile Edge Computing and Caching in Wireless Multicast Systems
In this paper, we present a novel mobile edge computing (MEC) model where the
MEC server has the input and output data of all computation tasks and
communicates with multiple caching-and-computing-enabled mobile devices via a
shared wireless link. Each task request can be served from local output
caching, local computing with input caching, local computing or MEC computing,
each of which incurs a unique bandwidth requirement of the multicast link.
Aiming to minimize the transmission bandwidth, we design and optimize the local
caching and computing policy at mobile devices subject to latency, caching,
energy and multicast transmission constraints. The joint policy optimization
problem is shown to be NP-hard. When the output data size is smaller than the
input data size, we reformulate the problem as minimization of a monotone
submodular function over matroid constraints and obtain the optimal solution
via a strongly polynomial algorithm of Schrijver. On the other hand, when the
output data size is larger than the input data size, by leveraging sample
approximation and concave convex procedure together with the alternating
direction method of multipliers, we propose a low-complexity high-performance
algorithm and prove it converges to a stationary point. Furthermore, we
theoretically reveal how much bandwidth gain can be achieved from computing and
caching resources at mobile devices or the multicast transmission for symmetric
case. Our results indicate that exploiting the computing and caching resources
at mobile devices as well as multicast transmission can provide significant
bandwidth savings.Comment: submitted to IEEE Trans. Wireless Communications. arXiv admin note:
text overlap with arXiv:1807.0553
Design and Optimization of VoD schemes with Client Caching in Wireless Multicast Networks
Due to the explosive growth in multimedia traffic, the scalability of
video-on-demand (VoD) services becomes increasingly important. By exploiting
the potential cache ability at the client side, the performance of VoD
multicast delivery can be improved through video segment pre-caching. In this
paper, we address the performance limits of client caching enabled VoD schemes
in wireless multicast networks with asynchronous requests. Both reactive and
proactive systems are investigated. Specifically, for the reactive system where
videos are transmitted on demand, we propose a joint cache allocation and
multicast delivery scheme to minimize the average bandwidth consumption under
the zero-delay constraint. For the proactive system where videos are
periodically broadcasted, a joint design of the cache-bandwidth allocation
algorithm and the delivery mechanism is developed to minimize the average
waiting time under the total bandwidth constraint. In addition to the full
access pattern where clients view videos in their entirety, we further consider
the access patterns with random endpoints, fixed-size intervals and downloading
demand, respectively. The impacts of different access patterns on the
resource-allocation algorithm and the delivery mechanism are elaborated.
Simulation results validate the accuracy of the analytical results and also
provide useful insights in designing VoD networks with client caching.Comment: accepted by IEEE Transactions on Vehicular Technolog
Delay Outage Probability of Multi-relay Selection for Mobile Relay Edge Computing Systems
In this paper, we deal with the problem of relay selection in mobile edge
computing networks, where a source node transmits a computation-intensive task
to a destination via the aid of multiple relay nodes. It differs from the
traditional relay nodes in the way that each relay node is equipped with an
edge computing server, thus each relay node can execute the received task and
forwards the computed result to the destination. Accordingly, we define a delay
outage probability to evaluate the impact of the relay computing ability on the
link communications, and then propose a latency-best relay selection (LBRS)
scheme that not only consider the communication capability, but also consider
the computing ability. The performance of the proposed relay selection scheme
with the traditional communication-only relay selection (CORS) and
computing-only selection (CPORS) schemes in terms of the delay outage
probability and the diversity order is analyzed, compared with other relay
selection schemes. We show that the proposed LBRS scheme reduces to the
traditional CORS scheme under the high signal-to-noise ratio (SNR) region. We
further reveal that the diversity orders of both the proposed LBRS and CORS
schemes are dependent on the computing ability of relay nodes.Comment: submitted to IEEE SPAWC 201
Communications-Caching-Computing Tradeoff Analysis for Bidirectional Data Computation in Mobile Edge Networks
With the advent of the modern mobile traffic, e.g., online gaming, augmented
reality delivery and etc., a novel bidirectional computation task model where
the input data of each task consists of two parts, one generated at the mobile
device in real-time and the other originated from the Internet proactively, is
emerging as an important use case of 5G. In this paper, for ease of analytical
analysis, we consider the homogeneous bidirectional computation task model in a
mobile edge network which consists of one mobile edge computing (MEC) server
and one mobile device, both enabled with computing and caching capabilities.
Each task can be served via three mechanisms, i.e., local computing with local
caching, local computing without local caching and computing at the MEC server.
To minimize the average bandwidth, we formulate the joint caching and computing
optimization problem under the latency, cache size and average power
constraints. We derive the closed-form expressions for the optimal policy and
the minimum bandwidth. The tradeoff among communications, computing and caching
is illustrated both analytically and numerically, which provides insightful
guideline for the network designers.Comment: the short version of this paper is submitted to IEEE ISIT 202
Modeling and Trade-off for Mobile Communication, Computing and Caching Networks
Computation task service delivery in a computing-enabled and caching-aided
multi-user mobile edge computing (MEC) system is studied in this paper, where a
MEC server can deliver the input or output datas of tasks to mobile devices
over a wireless multicast channel. The computing-enabled and caching-aided
mobile devices are able to store the input or output datas of some tasks, and
also compute some tasks locally, reducing the wireless bandwidth consumption.
The corresponding framework of this system is established, and under the
latency constraint, we jointly optimize the caching and computing policy at
mobile devices to minimize the required transmission bandwidth. The joint
policy optimization problem is shown to be NP-hard, and based on equivalent
transformation and exact penalization of the problem, a stationary point is
obtained via concave convex procedure (CCCP). Moreover, in a symmetric
scenario, gains offered by this approach are derived to analytically understand
the influences of caching and computing resources at mobile devices, multicast
transmission, the number of mobile devices, as well as the number of tasks on
the transmission bandwidth. Our results indicate that exploiting the computing
and caching resources at mobile devices can provide significant bandwidth
savings.Comment: to appear in IEEE GLOBECOM 201