998 research outputs found
Millimeter Wave Cellular Networks: A MAC Layer Perspective
The millimeter wave (mmWave) frequency band is seen as a key enabler of
multi-gigabit wireless access in future cellular networks. In order to overcome
the propagation challenges, mmWave systems use a large number of antenna
elements both at the base station and at the user equipment, which lead to high
directivity gains, fully-directional communications, and possible noise-limited
operations. The fundamental differences between mmWave networks and traditional
ones challenge the classical design constraints, objectives, and available
degrees of freedom. This paper addresses the implications that highly
directional communication has on the design of an efficient medium access
control (MAC) layer. The paper discusses key MAC layer issues, such as
synchronization, random access, handover, channelization, interference
management, scheduling, and association. The paper provides an integrated view
on MAC layer issues for cellular networks, identifies new challenges and
tradeoffs, and provides novel insights and solution approaches.Comment: 21 pages, 9 figures, 2 tables, to appear in IEEE Transactions on
Communication
Coverage Analysis of Relay Assisted Millimeter Wave Cellular Networks with Spatial Correlation
We propose a novel analytical framework for evaluating the coverage
performance of a millimeter wave (mmWave) cellular network where idle user
equipments (UEs) act as relays. In this network, the base station (BS) adopts
either the direct mode to transmit to the destination UE, or the relay mode if
the direct mode fails, where the BS transmits to the relay UE and then the
relay UE transmits to the destination UE. To address the drastic rotational
movements of destination UEs in practice, we propose to adopt selection
combining at destination UEs. New expression is derived for the
signal-to-interference-plus-noise ratio (SINR) coverage probability of the
network. Using numerical results, we first demonstrate the accuracy of our new
expression. Then we show that ignoring spatial correlation, which has been
commonly adopted in the literature, leads to severe overestimation of the SINR
coverage probability. Furthermore, we show that introducing relays into a
mmWave cellular network vastly improves the coverage performance. In addition,
we show that the optimal BS density maximizing the SINR coverage probability
can be determined by using our analysis
Self-Sustaining Caching Stations: Towards Cost-Effective 5G-Enabled Vehicular Networks
In this article, we investigate the cost-effective 5G-enabled vehicular
networks to support emerging vehicular applications, such as autonomous
driving, in-car infotainment and location-based road services. To this end,
self-sustaining caching stations (SCSs) are introduced to liberate on-road base
stations from the constraints of power lines and wired backhauls. Specifically,
the cache-enabled SCSs are powered by renewable energy and connected to core
networks through wireless backhauls, which can realize "drop-and-play"
deployment, green operation, and low-latency services. With SCSs integrated, a
5G-enabled heterogeneous vehicular networking architecture is further proposed,
where SCSs are deployed along roadside for traffic offloading while
conventional macro base stations (MBSs) provide ubiquitous coverage to
vehicles. In addition, a hierarchical network management framework is designed
to deal with high dynamics in vehicular traffic and renewable energy, where
content caching, energy management and traffic steering are jointly
investigated to optimize the service capability of SCSs with balanced power
demand and supply in different time scales. Case studies are provided to
illustrate SCS deployment and operation designs, and some open research issues
are also discussed.Comment: IEEE Communications Magazine, to appea
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