212 research outputs found
Degrees of Freedom of Two-Hop Wireless Networks: "Everyone Gets the Entire Cake"
We show that fully connected two-hop wireless networks with K sources, K
relays and K destinations have K degrees of freedom both in the case of
time-varying channel coefficients and in the case of constant channel
coefficients (in which case the result holds for almost all values of constant
channel coefficients). Our main contribution is a new achievability scheme
which we call Aligned Network Diagonalization. This scheme allows the data
streams transmitted by the sources to undergo a diagonal linear transformation
from the sources to the destinations, thus being received free of interference
by their intended destination. In addition, we extend our scheme to multi-hop
networks with fully connected hops, and multi-hop networks with MIMO nodes, for
which the degrees of freedom are also fully characterized.Comment: Presented at the 2012 Allerton Conference. Submitted to IEEE
Transactions on Information Theor
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
Communication-Aware Computing for Edge Processing
We consider a mobile edge computing problem, in which mobile users offload
their computation tasks to computing nodes (e.g., base stations) at the network
edge. The edge nodes compute the requested functions and communicate the
computed results to the users via wireless links. For this problem, we propose
a Universal Coded Edge Computing (UCEC) scheme for linear functions to
simultaneously minimize the load of computation at the edge nodes, and maximize
the physical-layer communication efficiency towards the mobile users. In the
proposed UCEC scheme, edge nodes create coded inputs of the users, from which
they compute coded output results. Then, the edge nodes utilize the computed
coded results to create communication messages that zero-force all the
interference signals over the air at each user. Specifically, the proposed
scheme is universal since the coded computations performed at the edge nodes
are oblivious of the channel states during the communication process from the
edge nodes to the users.Comment: To Appear in ISIT 201
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