65,444 research outputs found
Scaling Laws for Infrastructure Single and Multihop Wireless Networks in Wideband Regimes
With millimeter wave bands emerging as a strong candidate for 5G cellular
networks, next-generation systems may be in a unique position where spectrum is
plentiful. To assess the potential value of this spectrum, this paper derives
scaling laws on the per mobile downlink feasible rate with large bandwidth and
number of nodes, for both Infrastructure Single Hop (ISH) and Infrastructure
Multi-Hop (IMH) architectures. It is shown that, for both cases, there exist
\emph{critical bandwidth scalings} above which increasing the bandwidth no
longer increases the feasible rate per node. These critical thresholds coincide
exactly with the bandwidths where, for each architecture, the network
transitions from being degrees-of-freedom-limited to power-limited. For ISH,
this critical bandwidth threshold is lower than IMH when the number of users
per base station grows with network size. This result suggests that multi-hop
transmissions may be necessary to fully exploit large bandwidth degrees of
freedom in deployments with growing number of users per cell.Comment: 5 pages, 3 figure
Emergent Properties in Structurally Dynamic Disordered Cellular Networks
We relate structurally dynamic cellular networks, a class of models we
developed in fundamental space-time physics, to SDCA, introduced some time ago
by Ilachinski and Halpern. We emphasize the crucial property of a non-linear
interaction of network geometry with the matter degrees of freedom in order to
emulate the supposedly highly erratic and strongly fluctuating space-time
structure on the Planck scale. We then embark on a detailed numerical analysis
of various large scale characteristics of several classes of models in order to
understand what will happen if some sort of macroscopic or continuum limit is
performed. Of particular relevance in this context is a notion of network
dimension and its behavior in this limit. Furthermore, the possibility of phase
transitions is discussed.Comment: 20 pages, Latex, 6 figure
Elements of Cellular Blind Interference Alignment --- Aligned Frequency Reuse, Wireless Index Coding and Interference Diversity
We explore degrees of freedom (DoF) characterizations of partially connected
wireless networks, especially cellular networks, with no channel state
information at the transmitters. Specifically, we introduce three fundamental
elements --- aligned frequency reuse, wireless index coding and interference
diversity --- through a series of examples, focusing first on infinite regular
arrays, then on finite clusters with arbitrary connectivity and message sets,
and finally on heterogeneous settings with asymmetric multiple antenna
configurations. Aligned frequency reuse refers to the optimality of orthogonal
resource allocations in many cases, but according to unconventional reuse
patterns that are guided by interference alignment principles. Wireless index
coding highlights both the intimate connection between the index coding problem
and cellular blind interference alignment, as well as the added complexity
inherent to wireless settings. Interference diversity refers to the observation
that in a wireless network each receiver experiences a different set of
interferers, and depending on the actions of its own set of interferers, the
interference-free signal space at each receiver fluctuates differently from
other receivers, creating opportunities for robust applications of blind
interference alignment principles
Degrees of Freedom of Uplink-Downlink Multiantenna Cellular Networks
An uplink-downlink two-cell cellular network is studied in which the first
base station (BS) with antennas receives independent messages from its
serving users, while the second BS with antennas transmits
independent messages to its serving users. That is, the first and second
cells operate as uplink and downlink, respectively. Each user is assumed to
have a single antenna. Under this uplink-downlink setting, the sum degrees of
freedom (DoF) is completely characterized as the minimum of
,
, , and , where denotes
. The result demonstrates that, for a broad class of network
configurations, operating one of the two cells as uplink and the other cell as
downlink can strictly improve the sum DoF compared to the conventional uplink
or downlink operation, in which both cells operate as either uplink or
downlink. The DoF gain from such uplink-downlink operation is further shown to
be achievable for heterogeneous cellular networks having hotspots and with
delayed channel state information.Comment: 22 pages, 11 figures, in revision for IEEE Transactions on
Information Theor
Improving Macrocell - Small Cell Coexistence through Adaptive Interference Draining
The deployment of underlay small base stations (SBSs) is expected to
significantly boost the spectrum efficiency and the coverage of next-generation
cellular networks. However, the coexistence of SBSs underlaid to an existing
macro-cellular network faces important challenges, notably in terms of spectrum
sharing and interference management. In this paper, we propose a novel
game-theoretic model that enables the SBSs to optimize their transmission rates
by making decisions on the resource occupation jointly in the frequency and
spatial domains. This procedure, known as interference draining, is performed
among cooperative SBSs and allows to drastically reduce the interference
experienced by both macro- and small cell users. At the macrocell side, we
consider a modified water-filling policy for the power allocation that allows
each macrocell user (MUE) to focus the transmissions on the degrees of freedom
over which the MUE experiences the best channel and interference conditions.
This approach not only represents an effective way to decrease the received
interference at the MUEs but also grants the SBSs tier additional transmission
opportunities and allows for a more agile interference management. Simulation
results show that the proposed approach yields significant gains at both
macrocell and small cell tiers, in terms of average achievable rate per user,
reaching up to 37%, relative to the non-cooperative case, for a network with
150 MUEs and 200 SBSs
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