22 research outputs found
The Capacity Region of the Restricted Two-Way Relay Channel with Any Deterministic Uplink
This paper considers the two-way relay channel (TWRC) where two users
communicate via a relay. For the restricted TWRC where the uplink from the
users to the relay is any deterministic function and the downlink from the
relay to the users is any arbitrary channel, the capacity region is obtained.
The TWRC considered is restricted in the sense that each user can only transmit
a function of its message.Comment: author's final version (accepted and to appear in IEEE Communications
Letters
The Finite Field Multi-Way Relay Channel with Correlated Sources: Beyond Three Users
The multi-way relay channel (MWRC) models cooperative communication networks
in which many users exchange messages via a relay. In this paper, we consider
the finite field MWRC with correlated messages. The problem is to find all
achievable rates, defined as the number of channel uses required per reliable
exchange of message tuple. For the case of three users, we have previously
established that for a special class of source distributions, the set of all
achievable rates can be found [Ong et al., ISIT 2010]. The class is specified
by an almost balanced conditional mutual information (ABCMI) condition. In this
paper, we first generalize the ABCMI condition to the case of more than three
users. We then show that if the sources satisfy the ABCMI condition, then the
set of all achievable rates is found and can be attained using a separate
source-channel coding architecture.Comment: Author's final version (to be presented at ISIT 2012
The Finite Field Multi-Way Relay Channel with Correlated Sources: The Three-User Case
The three-user finite field multi-way relay channel with correlated sources
is considered. The three users generate possibly correlated messages, and each
user is to transmit its message to the two other users reliably in the Shannon
sense. As there is no direct link among the users, communication is carried out
via a relay, and the link from the users to the relay and those from the relay
to the users are finite field adder channels with additive noise of arbitrary
distribution. The problem is to determine the set of all possible achievable
rates, defined as channel uses per source symbol for reliable communication.
For two classes of source/channel combinations, the solution is obtained using
Slepian-Wolf source coding combined with functional-decode-forward channel
coding.Comment: to be presented at ISIT 201
The Capacity Region of Restricted Multi-Way Relay Channels with Deterministic Uplinks
This paper considers the multi-way relay channel (MWRC) where multiple users
exchange messages via a single relay. The capacity region is derived for a
special class of MWRCs where (i) the uplink and the downlink are separated in
the sense that there is no direct user-to-user links, (ii) the channel is
restricted in the sense that each user's transmitted channel symbols can depend
on only its own message, but not on its received channel symbols, and (iii) the
uplink is any deterministic function.Comment: Author's final version (to be presented at ISIT 2012
On the Achievable Rates of Pairwise Multiway Relay Channels
In this paper, we study the effect of users' transmission ordering on the
common rate and sum rate of pairwise multiway relay channels (MWRCs) with
functional-decode-forward strategy. To this end, we first develop a graphical
model for the data transmission in a pairwise MWRC. Using this model, we then
find the optimal orderings that achieve the maximum common rate and sum rate of
the system. The achieved maximum common and sum rate are also found. Moreover,
we show that the performance gap between optimal orderings and a random
ordering vanishes when SNR increases. Computer simulations are presented for
better illustration of the results.Comment: Extended version of "On the Achievable Rates of Pairwise Multiway
Relay Channels" accepted for ISIT 201
Optimal Coding Functions for Pairwise Message Sharing on Finite-Field Multi-Way Relay Channels
This paper considers the finite-field multi-way relay channel with pairwise
message sharing, where multiple users exchange messages through a single relay
and where the users may share parts of their source messages (meaning that some
message parts are known/common to more than one user). In this paper, we design
an optimal functional-decode-forward coding scheme that takes the shared
messages into account. More specifically, we design an optimal function for the
relay to decode (from the users on the uplink) and forward (back to the users
on the downlink). We then show that this proposed function-decode-forward
coding scheme can achieve the capacity region of the finite-field multi-way
relay channel with pairwise message sharing. This paper generalizes our
previous result for the case of three users to any number of users.Comment: Author's final version (accepted for presentation at the 2014 IEEE
International Conference on Communications [ICC 2014]
The Three-User Finite-Field Multi-Way Relay Channel with Correlated Sources
This paper studies the three-user finite-field multi-way relay channel, where
the users exchange messages via a relay. The messages are arbitrarily
correlated, and the finite-field channel is linear and is subject to additive
noise of arbitrary distribution. The problem is to determine the minimum
achievable source-channel rate, defined as channel uses per source symbol
needed for reliable communication. We combine Slepian-Wolf source coding and
functional-decode-forward channel coding to obtain the solution for two classes
of source and channel combinations. Furthermore, for correlated sources that
have their common information equal their mutual information, we propose a new
coding scheme to achieve the minimum source-channel rate.Comment: Author's final version (accepted and to appear in IEEE Transactions
on Communications
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