65,227 research outputs found
Coverage and Deployment Analysis of Narrowband Internet of Things in the Wild
Narrowband Internet of Things (NB-IoT) is gaining momentum as a promising
technology for massive Machine Type Communication (mMTC). Given that its
deployment is rapidly progressing worldwide, measurement campaigns and
performance analyses are needed to better understand the system and move toward
its enhancement. With this aim, this paper presents a large scale measurement
campaign and empirical analysis of NB-IoT on operational networks, and
discloses valuable insights in terms of deployment strategies and radio
coverage performance. The reported results also serve as examples showing the
potential usage of the collected dataset, which we make open-source along with
a lightweight data visualization platform.Comment: Accepted for publication in IEEE Communications Magazine (Internet of
Things and Sensor Networks Series
Content Caching and Delivery over Heterogeneous Wireless Networks
Emerging heterogeneous wireless architectures consist of a dense deployment
of local-coverage wireless access points (APs) with high data rates, along with
sparsely-distributed, large-coverage macro-cell base stations (BS). We design a
coded caching-and-delivery scheme for such architectures that equips APs with
storage, enabling content pre-fetching prior to knowing user demands. Users
requesting content are served by connecting to local APs with cached content,
as well as by listening to a BS broadcast transmission. For any given content
popularity profile, the goal is to design the caching-and-delivery scheme so as
to optimally trade off the transmission cost at the BS against the storage cost
at the APs and the user cost of connecting to multiple APs. We design a coded
caching scheme for non-uniform content popularity that dynamically allocates
user access to APs based on requested content. We demonstrate the approximate
optimality of our scheme with respect to information-theoretic bounds. We
numerically evaluate it on a YouTube dataset and quantify the trade-off between
transmission rate, storage, and access cost. Our numerical results also suggest
the intriguing possibility that, to gain most of the benefits of coded caching,
it suffices to divide the content into a small number of popularity classes.Comment: A shorter version is to appear in IEEE INFOCOM 201
Near-Memory Address Translation
Memory and logic integration on the same chip is becoming increasingly cost
effective, creating the opportunity to offload data-intensive functionality to
processing units placed inside memory chips. The introduction of memory-side
processing units (MPUs) into conventional systems faces virtual memory as the
first big showstopper: without efficient hardware support for address
translation MPUs have highly limited applicability. Unfortunately, conventional
translation mechanisms fall short of providing fast translations as
contemporary memories exceed the reach of TLBs, making expensive page walks
common.
In this paper, we are the first to show that the historically important
flexibility to map any virtual page to any page frame is unnecessary in today's
servers. We find that while limiting the associativity of the
virtual-to-physical mapping incurs no penalty, it can break the
translate-then-fetch serialization if combined with careful data placement in
the MPU's memory, allowing for translation and data fetch to proceed
independently and in parallel. We propose the Distributed Inverted Page Table
(DIPTA), a near-memory structure in which the smallest memory partition keeps
the translation information for its data share, ensuring that the translation
completes together with the data fetch. DIPTA completely eliminates the
performance overhead of translation, achieving speedups of up to 3.81x and
2.13x over conventional translation using 4KB and 1GB pages respectively.Comment: 15 pages, 9 figure
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