1,644 research outputs found
Interference Channels with Destination Cooperation
Interference is a fundamental feature of the wireless channel. To better
understand the role of cooperation in interference management, the two-user
Gaussian interference channel where the destination nodes can cooperate by
virtue of being able to both transmit and receive is studied. The sum-capacity
of this channel is characterized up to a constant number of bits. The coding
scheme employed builds up on the superposition scheme of Han and Kobayashi
(1981) for two-user interference channels without cooperation. New upperbounds
to the sum-capacity are also derived.Comment: revised based on reviewers' comment
Relays for Interference Mitigation in Wireless Networks
Wireless links play an important role in the last mile network connectivity. In contrast to the strictly centralized approach of today's wireless systems, the future promises decentralization of network management. Nodes potentially engage in localized grouping and organization based on their neighborhood to carry out complex goals such as end-to-end communication. The quadratic energy dissipation of the wireless medium necessitates the presence of certain relay nodes in the network. Conventionally, the role of such relays is limited to passing messages in a chain in a point-point hopping architecture. With the decentralization, multiple nodes could potentially interfere with each other. This work proposes a technique to exploit the presence of relays in a way that mitigates interference between the network nodes. Optimal spatial locations and transmission schemes which enhance this gain are identified
On the Outage Probability of the Full-Duplex Interference-Limited Relay Channel
In this paper, we study the performance, in terms of the asymptotic error
probability, of a user which communicates with a destination with the aid of a
full-duplex in-band relay. We consider that the network is
interference-limited, and interfering users are distributed as a Poisson point
process. In this case, the asymptotic error probability is upper bounded by the
outage probability (OP). We investigate the outage behavior for well-known
cooperative schemes, namely, decode-and-forward (DF) and compress-and-forward
(CF) considering fading and path loss. For DF we determine the exact OP and
develop upper bounds which are tight in typical operating conditions. Also, we
find the correlation coefficient between source and relay signals which
minimizes the OP when the density of interferers is small. For CF, the
achievable rates are determined by the spatial correlation of the
interferences, and a straightforward analysis isn't possible. To handle this
issue, we show the rate with correlated noises is at most one bit worse than
with uncorrelated noises, and thus find an upper bound on the performance of
CF. These results are useful to evaluate the performance and to optimize
relaying schemes in the context of full-duplex wireless networks.Comment: 30 pages, 4 figures. Final version. To appear in IEEE JSAC Special
Issue on Full-duplex Wireless Communications and Networks, 201
On Joint Source-Channel Coding for Correlated Sources Over Multiple-Access Relay Channels
We study the transmission of correlated sources over discrete memoryless (DM)
multiple-access-relay channels (MARCs), in which both the relay and the
destination have access to side information arbitrarily correlated with the
sources. As the optimal transmission scheme is an open problem, in this work we
propose a new joint source-channel coding scheme based on a novel combination
of the correlation preserving mapping (CPM) technique with Slepian-Wolf (SW)
source coding, and obtain the corresponding sufficient conditions. The proposed
coding scheme is based on the decode-and-forward strategy, and utilizes CPM for
encoding information simultaneously to the relay and the destination, whereas
the cooperation information from the relay is encoded via SW source coding. It
is shown that there are cases in which the new scheme strictly outperforms the
schemes available in the literature. This is the first instance of a
source-channel code that uses CPM for encoding information to two different
nodes (relay and destination). In addition to sufficient conditions, we present
three different sets of single-letter necessary conditions for reliable
transmission of correlated sources over DM MARCs. The newly derived conditions
are shown to be at least as tight as the previously known necessary conditions.Comment: Accepted to TI
Relaying for Multiuser Networks in the Absence of Codebook Information
This work considers relay assisted transmission for multiuser networks when
the relay has no access to the codebooks used by the transmitters. The relay is
called oblivious for this reason. Of particular interest is the generalized
compress-and-forward (GCF) strategy, where the destinations jointly decode the
compression indices and the transmitted messages, and their optimality in this
setting. The relay-to-destination links are assumed to be out-of-band with
finite capacity. Two models are investigated: the multiple access relay channel
(MARC) and the interference relay channel (IFRC). For the MARC with an
oblivious relay, a new outerbound is derived and it is shown to be tight by
means of achievability of the capacity region using GCF scheme. For the IFRC
with an oblivious relay, a new strong interference condition is established,
under which the capacity region is found by deriving a new outerbound and
showing that it is achievable using GCF scheme. The result is further extended
to establish the capacity region of M-user MARC with an oblivious relay, and
multicast networks containing M sources and K destinations with an oblivious
relay.Comment: submitted to IEEE Transactions on Information Theor
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
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