2,038 research outputs found
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
Reliable Physical Layer Network Coding
When two or more users in a wireless network transmit simultaneously, their
electromagnetic signals are linearly superimposed on the channel. As a result,
a receiver that is interested in one of these signals sees the others as
unwanted interference. This property of the wireless medium is typically viewed
as a hindrance to reliable communication over a network. However, using a
recently developed coding strategy, interference can in fact be harnessed for
network coding. In a wired network, (linear) network coding refers to each
intermediate node taking its received packets, computing a linear combination
over a finite field, and forwarding the outcome towards the destinations. Then,
given an appropriate set of linear combinations, a destination can solve for
its desired packets. For certain topologies, this strategy can attain
significantly higher throughputs over routing-based strategies. Reliable
physical layer network coding takes this idea one step further: using
judiciously chosen linear error-correcting codes, intermediate nodes in a
wireless network can directly recover linear combinations of the packets from
the observed noisy superpositions of transmitted signals. Starting with some
simple examples, this survey explores the core ideas behind this new technique
and the possibilities it offers for communication over interference-limited
wireless networks.Comment: 19 pages, 14 figures, survey paper to appear in Proceedings of the
IEE
Multi-Source Cooperative Communication with Opportunistic Interference Cancelling Relays
In this paper we present a multi-user cooperative protocol for wireless
networks. Two sources transmit simultaneously their information blocks and
relays employ opportunistically successive interference cancellation (SIC) in
an effort to decode them. An adaptive decode/amplify-and-forward scheme is
applied at the relays to the decoded blocks or their sufficient statistic if
decoding fails. The main feature of the protocol is that SIC is exploited in a
network since more opportunities arise for each block to be decoded as the
number of used relays NRU is increased. This feature leads to benefits in terms
of diversity and multiplexing gains that are proven with the help of an
analytical outage model and a diversity-multiplexing tradeoff (DMT) analysis.
The performance improvements are achieved without any network synchronization
and coordination. In the final part of this work the closed-form outage
probability model is used by a novel approach for offline pre-selection of the
NRU relays, that have the best SIC performance, from a larger number of NR
nodes. The analytical results are corroborated with extensive simulations,
while the protocol is compared with orthogonal and multi-user protocols
reported in the literature.Comment: in IEEE Transactions on Communications, 201
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