4 research outputs found
Myopic Coding in Multiterminal Networks
This paper investigates the interplay between cooperation and achievable
rates in multi-terminal networks. Cooperation refers to the process of nodes
working together to relay data toward the destination. There is an inherent
tradeoff between achievable information transmission rates and the level of
cooperation, which is determined by how many nodes are involved and how the
nodes encode/decode the data. We illustrate this trade-off by studying
information-theoretic decode-forward based coding strategies for data
transmission in multi-terminal networks. Decode-forward strategies are usually
discussed in the context of omniscient coding, in which all nodes in the
network fully cooperate with each other, both in encoding and decoding. In this
paper, we investigate myopic coding, in which each node cooperates with only a
few neighboring nodes. We show that achievable rates of myopic decode-forward
can be as large as that of omniscient decode-forward in the low SNR regime. We
also show that when each node has only a few cooperating neighbors, adding one
node into the cooperation increases the transmission rate significantly.
Furthermore, we show that myopic decode-forward can achieve non-zero rates as
the network size grows without bound
On Capacity and Optimal Scheduling for the Half-Duplex Multiple-Relay Channel
We study the half-duplex multiple-relay channel (HD-MRC) where every node can
either transmit or listen but cannot do both at the same time. We obtain a
capacity upper bound based on a max-flow min-cut argument and achievable
transmission rates based on the decode-forward (DF) coding strategy, for both
the discrete memoryless HD-MRC and the phase-fading HD-MRC. We discover that
both the upper bound and the achievable rates are functions of the
transmit/listen state (a description of which nodes transmit and which
receive). More precisely, they are functions of the time fraction of the
different states, which we term a schedule. We formulate the optimal scheduling
problem to find an optimal schedule that maximizes the DF rate. The optimal
scheduling problem turns out to be a maximin optimization, for which we propose
an algorithmic solution. We demonstrate our approach on a four-node
multiple-relay channel, obtaining closed-form solutions in certain scenarios.
Furthermore, we show that for the received signal-to-noise ratio degraded
phase-fading HD-MRC, the optimal scheduling problem can be simplified to a max
optimization.Comment: Author's final version (to appear in IEEE Transactions on Information
Theory
Cooperative coding and routing in multiple-terminal wireless networks
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