23,179 research outputs found
Rate regions for coherent and noncoherent multisource network error correction
In this paper we derive capacity regions for network error correction with both known and unknown topologies (coherent and non-coherent network coding) under a multiple-source multicast transmission scenario. For the multiple-source non-multicast scenario, given any achievable network code for the error-free case, we construct a code with a reduced rate region for the case with errors
On Design of Collaborative Beamforming for Two-Way Relay Networks
We consider a two-way relay network, where two source nodes, S1 and S2,
exchange information through a cluster of relay nodes. The relay nodes receive
the sum signal from S1 and S2 in the first time slot. In the second time slot,
each relay node multiplies its received signal by a complex coefficient and
retransmits the signal to the two source nodes, which leads to a collaborative
two-way beamforming system. By applying the principle of analog network coding,
each receiver at S1 and S2 cancels the "self-interference" in the received
signal from the relay cluster and decodes the message. This paper studies the
2-dimensional achievable rate region for such a two-way relay network with
collaborative beamforming. With different assumptions of channel reciprocity
between the source-relay and relay-source channels, the achievable rate region
is characterized under two setups. First, with reciprocal channels, we
investigate the achievable rate regions when the relay cluster is subject to a
sum-power constraint or individual-power constraints. We show that the optimal
beamforming vectors obtained from solving the weighted sum inverse-SNR
minimization (WSISMin) problems are sufficient to characterize the
corresponding achievable rate region. Furthermore, we derive the closed form
solutions for those optimal beamforming vectors and consequently propose the
partially distributed algorithms to implement the optimal beamforming, where
each relay node only needs the local channel information and one global
parameter. Second, with the non-reciprocal channels, the achievable rate
regions are also characterized for both the sum-power constraint case and the
individual-power constraint case. Although no closed-form solutions are
available under this setup, we present efficient numerical algorithms.Comment: new version of the previously posted, single column double spacing,
24 page
Polar codes in network quantum information theory
Polar coding is a method for communication over noisy classical channels
which is provably capacity-achieving and has an efficient encoding and
decoding. Recently, this method has been generalized to the realm of quantum
information processing, for tasks such as classical communication, private
classical communication, and quantum communication. In the present work, we
apply the polar coding method to network quantum information theory, by making
use of recent advances for related classical tasks. In particular, we consider
problems such as the compound multiple access channel and the quantum
interference channel. The main result of our work is that it is possible to
achieve the best known inner bounds on the achievable rate regions for these
tasks, without requiring a so-called quantum simultaneous decoder. Thus, our
work paves the way for developing network quantum information theory further
without requiring a quantum simultaneous decoder.Comment: 18 pages, 2 figures, v2: 10 pages, double column, version accepted
for publicatio
The Multi-way Relay Channel
The multiuser communication channel, in which multiple users exchange
information with the help of a relay terminal, termed the multi-way relay
channel (mRC), is introduced. In this model, multiple interfering clusters of
users communicate simultaneously, where the users within the same cluster wish
to exchange messages among themselves. It is assumed that the users cannot
receive each other's signals directly, and hence the relay terminal in this
model is the enabler of communication. In particular, restricted encoders,
which ignore the received channel output and use only the corresponding
messages for generating the channel input, are considered. Achievable rate
regions and an outer bound are characterized for the Gaussian mRC, and their
comparison is presented in terms of exchange rates in a symmetric Gaussian
network scenario. It is shown that the compress-and-forward (CF) protocol
achieves exchange rates within a constant bit offset of the exchange capacity
independent of the power constraints of the terminals in the network. A finite
bit gap between the exchange rates achieved by the CF and the
amplify-and-forward (AF) protocols is also shown. The two special cases of the
mRC, the full data exchange model, in which every user wants to receive
messages of all other users, and the pairwise data exchange model which
consists of multiple two-way relay channels, are investigated in detail. In
particular for the pairwise data exchange model, in addition to the proposed
random coding based achievable schemes, a nested lattice coding based scheme is
also presented and is shown to achieve exchange rates within a constant bit gap
of the exchange capacity.Comment: Revised version of our submission to the Transactions on Information
Theor
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