6,352 research outputs found
LTE and Wi-Fi Coexistence in Unlicensed Spectrum with Application to Smart Grid: A Review
Long Term Evolution (LTE) is expanding its utilization in unlicensed band by
deploying LTE Unlicensed (LTEU) and Licensed Assisted Access LTE (LTE-LAA)
technology. Smart Grid can take the advantages of unlicensed bands for
achieving two-way communication between smart meters and utility data centers
by using LTE-U/LTE-LAA. However, both schemes must co-exist with the incumbent
Wi-Fi system. In this paper, several co-existence schemes of Wi-Fi and LTE
technology is comprehensively reviewed. The challenges of deploying LTE and
Wi-Fi in the same band are clearly addressed based on the papers reviewed.
Solution procedures and techniques to resolve the challenging issues are
discussed in a short manner. The performance of various network architectures
such as listenbefore- talk (LBT) based LTE, carrier sense multiple access with
collision avoidance (CSMA/CA) based Wi-Fi is briefly compared. Finally, an
attempt is made to implement these proposed LTEWi- Fi models in smart grid
technology.Comment: submitted in 2018 IEEE PES T&
Uncoordinated access schemes for the IoT: approaches, regulations, and performance
Internet of Things (IoT) devices communicate using a variety of protocols,
differing in many aspects, with the channel access method being one of the most
important. Most of the transmission technologies explicitly designed for IoT
and Machine-to-Machine (M2M) communication use either an ALOHA-based channel
access or some type of Listen Before Talk (LBT) strategy, based on carrier
sensing. In this paper, we provide a comparative overview of the uncoordinated
channel access methods for IoT technologies, namely ALOHA-based and LBT
schemes, in relation with the ETSI and FCC regulatory frameworks. Furthermore,
we provide a performance comparison of these access schemes, both in terms of
successful transmissions and energy efficiency, in a typical IoT deployment.
Results show that LBT is effective in reducing inter-node interference even for
long-range transmissions, though the energy efficiency can be lower than that
provided by ALOHA methods. The adoption of rate-adaptation schemes,
furthermore, lowers the energy consumption while improving the fairness among
nodes at different distances from the receiver. Coexistence issues are also
investigated, showing that in massive deployments LBT is severely affected by
the presence of ALOHA devices in the same area
Hybrid Spectrum Sharing in mmWave Cellular Networks
While spectrum at millimeter wave (mmWave) frequencies is less scarce than at
traditional frequencies below 6 GHz, still it is not unlimited, in particular
if we consider the requirements from other services using the same band and the
need to license mmWave bands to multiple mobile operators. Therefore, an
efficient spectrum access scheme is critical to harvest the maximum benefit
from emerging mmWave technologies. In this paper, we introduce a new hybrid
spectrum access scheme for mmWave networks, where data is aggregated through
two mmWave carriers with different characteristics. In particular, we consider
the case of a hybrid spectrum scheme between a mmWave band with exclusive
access and a mmWave band where spectrum is pooled between multiple operators.
To the best of our knowledge, this is the first study proposing hybrid spectrum
access for mmWave networks and providing a quantitative assessment of its
benefits. Our results show that this approach provides major advantages with
respect to traditional fully licensed or fully unlicensed spectrum access
schemes, though further work is needed to achieve a more complete understanding
of both technical and non technical implications
Survey of Spectrum Sharing for Inter-Technology Coexistence
Increasing capacity demands in emerging wireless technologies are expected to
be met by network densification and spectrum bands open to multiple
technologies. These will, in turn, increase the level of interference and also
result in more complex inter-technology interactions, which will need to be
managed through spectrum sharing mechanisms. Consequently, novel spectrum
sharing mechanisms should be designed to allow spectrum access for multiple
technologies, while efficiently utilizing the spectrum resources overall.
Importantly, it is not trivial to design such efficient mechanisms, not only
due to technical aspects, but also due to regulatory and business model
constraints. In this survey we address spectrum sharing mechanisms for wireless
inter-technology coexistence by means of a technology circle that incorporates
in a unified, system-level view the technical and non-technical aspects. We
thus systematically explore the spectrum sharing design space consisting of
parameters at different layers. Using this framework, we present a literature
review on inter-technology coexistence with a focus on wireless technologies
with equal spectrum access rights, i.e. (i) primary/primary, (ii)
secondary/secondary, and (iii) technologies operating in a spectrum commons.
Moreover, we reflect on our literature review to identify possible spectrum
sharing design solutions and performance evaluation approaches useful for
future coexistence cases. Finally, we discuss spectrum sharing design
challenges and suggest future research directions
Enhancing Coexistence in the Unlicensed Band with Massive MIMO
We consider cellular base stations (BSs) equipped with a large number of
antennas and operating in the unlicensed band. We denote such system as massive
MIMO unlicensed (mMIMO-U). We design the key procedures required to guarantee
coexistence between a cellular BS and nearby Wi-Fi devices. These include:
neighboring Wi-Fi channel covariance estimation, allocation of spatial degrees
of freedom for interference suppression, and enhanced channel sensing and data
transmission phases. We evaluate the performance of the so-designed mMIMO-U,
showing that it allows simultaneous cellular and Wi-Fi transmissions by keeping
their mutual interference below the regulatory threshold. The same is not true
for conventional listen-before-talk (LBT) operations. As a result, mMIMO-U
boosts the aggregate cellular-plus-Wi-Fi data rate in the unlicensed band with
respect to conventional LBT, exhibiting increasing gains as the number of BS
antennas grows.Comment: To appear in Proc. IEEE ICC 201
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