191 research outputs found
Toward End-to-End, Full-Stack 6G Terahertz Networks
Recent evolutions in semiconductors have brought the terahertz band in the
spotlight as an enabler for terabit-per-second communications in 6G networks.
Most of the research so far, however, has focused on understanding the physics
of terahertz devices, circuitry and propagation, and on studying physical layer
solutions. However, integrating this technology in complex mobile networks
requires a proper design of the full communication stack, to address link- and
system-level challenges related to network setup, management, coordination,
energy efficiency, and end-to-end connectivity. This paper provides an overview
of the issues that need to be overcome to introduce the terahertz spectrum in
mobile networks, from a MAC, network and transport layer perspective, with
considerations on the performance of end-to-end data flows on terahertz
connections.Comment: Published on IEEE Communications Magazine, THz Communications: A
Catalyst for the Wireless Future, 7 pages, 6 figure
MAC-Oriented Programmable Terahertz PHY via Graphene-based Yagi-Uda Antennas
Graphene is enabling a plethora of applications in a wide range of fields due
to its unique electrical, mechanical, and optical properties. In the realm of
wireless communications, graphene shows great promise for the implementation of
miniaturized and tunable antennas in the terahertz band. These unique
advantages open the door to new reconfigurable antenna structures which, in
turn, enable novel communication protocols at different levels of the stack.
This paper explores both aspects by, first, presenting a terahertz
Yagi-Uda-like antenna concept that achieves reconfiguration both in frequency
and beam direction simultaneously. Then, a programmable antenna controller
design is proposed to expose the reconfigurability to the PHY and MAC layers,
and several examples of its applicability are given. The performance and cost
of the proposed scheme is evaluated through full-wave simulations and
comparative analysis, demonstrating reconfigurability at nanosecond granularity
with overheads below 0.02 mm and 0.2 mW.Comment: Accepted for presentation in IEEE WCNC '1
MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey
Multi-beam antenna technologies have provided lots of promising solutions to
many current challenges faced in wireless mesh networks. The antenna can
establish several beamformings simultaneously and initiate concurrent
transmissions or receptions using multiple beams, thereby increasing the
overall throughput of the network transmission. Multi-beam antenna has the
ability to increase the spatial reuse, extend the transmission range, improve
the transmission reliability, as well as save the power consumption.
Traditional Medium Access Control (MAC) protocols for wireless network largely
relied on the IEEE 802.11 Distributed Coordination Function(DCF) mechanism,
however, IEEE 802.11 DCF cannot take the advantages of these unique
capabilities provided by multi-beam antennas. This paper surveys the MAC
protocols for wireless mesh networks with multi-beam antennas. The paper first
discusses some basic information in designing multi-beam antenna system and MAC
protocols, and then presents the main challenges for the MAC protocols in
wireless mesh networks compared with the traditional MAC protocols. A
qualitative comparison of the existing MAC protocols is provided to highlight
their novel features, which provides a reference for designing the new MAC
protocols. To provide some insights on future research, several open issues of
MAC protocols are discussed for wireless mesh networks using multi-beam
antennas.Comment: 22 pages, 6 figures, Future of Information and Communication
Conference (FICC) 2019, https://doi.org/10.1007/978-3-030-12388-8_
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
Beam-searching and Transmission Scheduling in Millimeter Wave Communications
Millimeter wave (mmW) wireless networks are capable to support multi-gigabit
data rates, by using directional communications with narrow beams. However,
existing mmW communications standards are hindered by two problems: deafness
and single link scheduling. The deafness problem, that is, a misalignment
between transmitter and receiver beams, demands a time consuming beam-searching
operation, which leads to an alignment-throughput tradeoff. Moreover, the
existing mmW standards schedule a single link in each time slot and hence do
not fully exploit the potential of mmW communications, where directional
communications allow multiple concurrent transmissions. These two problems are
addressed in this paper, where a joint beamwidth selection and power allocation
problem is formulated by an optimization problem for short range mmW networks
with the objective of maximizing effective network throughput. This
optimization problem allows establishing the fundamental alignment-throughput
tradeoff, however it is computationally complex and requires exact knowledge of
network topology, which may not be available in practice. Therefore, two
standard-compliant approximation solution algorithms are developed, which rely
on underestimation and overestimation of interference. The first one exploits
directionality to maximize the reuse of available spectrum and thereby
increases the network throughput, while imposing almost no computational
complexity. The second one is a more conservative approach that protects all
active links from harmful interference, yet enhances the network throughput by
100% compared to the existing standards. Extensive performance analysis
provides useful insights on the directionality level and the number of
concurrent transmissions that should be pursued. Interestingly, extremely
narrow beams are in general not optimal.Comment: 5 figures, 7 pages, accepted in ICC 201
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