2,117 research outputs found
Dynamic algorithms for multicast with intra-session network coding
The problem of multiple multicast sessions with
intra-session network coding in time-varying networks is considered.
The network-layer capacity region of input rates that can be
stably supported is established. Dynamic algorithms for multicast
routing, network coding, power allocation, session scheduling, and
rate allocation across correlated sources, which achieve stability
for rates within the capacity region, are presented. This work
builds on the back-pressure approach introduced by Tassiulas
et al., extending it to network coding and correlated sources. In
the proposed algorithms, decisions on routing, network coding,
and scheduling between different sessions at a node are made
locally at each node based on virtual queues for different sinks.
For correlated sources, the sinks locally determine and control
transmission rates across the sources. The proposed approach
yields a completely distributed algorithm for wired networks.
In the wireless case, power control among different transmitters
is centralized while routing, network coding, and scheduling
between different sessions at a given node are distributed
Towards Optimal Distributed Node Scheduling in a Multihop Wireless Network through Local Voting
In a multihop wireless network, it is crucial but challenging to schedule
transmissions in an efficient and fair manner. In this paper, a novel
distributed node scheduling algorithm, called Local Voting, is proposed. This
algorithm tries to semi-equalize the load (defined as the ratio of the queue
length over the number of allocated slots) through slot reallocation based on
local information exchange. The algorithm stems from the finding that the
shortest delivery time or delay is obtained when the load is semi-equalized
throughout the network. In addition, we prove that, with Local Voting, the
network system converges asymptotically towards the optimal scheduling.
Moreover, through extensive simulations, the performance of Local Voting is
further investigated in comparison with several representative scheduling
algorithms from the literature. Simulation results show that the proposed
algorithm achieves better performance than the other distributed algorithms in
terms of average delay, maximum delay, and fairness. Despite being distributed,
the performance of Local Voting is also found to be very close to a centralized
algorithm that is deemed to have the optimal performance
On the Achievable Rates of Multihop Virtual Full-Duplex Relay Channels
We study a multihop "virtual" full-duplex relay channel as a special case of
a general multiple multicast relay network. For such channel,
quantize-map-and-forward (QMF) (or noisy network coding (NNC)) achieves the
cut-set upper bound within a constant gap where the gap grows {\em linearly}
with the number of relay stages . However, this gap may not be negligible
for the systems with multihop transmissions (i.e., a wireless backhaul
operating at higher frequencies). We have recently attained an improved result
to the capacity scaling where the gap grows {\em logarithmically} as ,
by using an optimal quantization at relays and by exploiting relays' messages
(decoded in the previous time slot) as side-information. In this paper, we
further improve the performance of this network by presenting a mixed scheme
where each relay can perform either decode-and-forward (DF) or QMF with
possibly rate-splitting. We derive the achievable rate and show that the
proposed scheme outperforms the QMF-optimized scheme. Furthermore, we
demonstrate that this performance improvement increases with .Comment: To be presented at ISIT 201
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