962 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 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
Divide-and-conquer: Approaching the capacity of the two-pair bidirectional Gaussian relay network
The capacity region of multi-pair bidirectional relay networks, in which a
relay node facilitates the communication between multiple pairs of users, is
studied. This problem is first examined in the context of the linear shift
deterministic channel model. The capacity region of this network when the relay
is operating at either full-duplex mode or half-duplex mode for arbitrary
number of pairs is characterized. It is shown that the cut-set upper-bound is
tight and the capacity region is achieved by a so called divide-and-conquer
relaying strategy. The insights gained from the deterministic network are then
used for the Gaussian bidirectional relay network. The strategy in the
deterministic channel translates to a specific superposition of lattice codes
and random Gaussian codes at the source nodes and successive interference
cancelation at the receiving nodes for the Gaussian network. The achievable
rate of this scheme with two pairs is analyzed and it is shown that for all
channel gains it achieves to within 3 bits/sec/Hz per user of the cut-set
upper-bound. Hence, the capacity region of the two-pair bidirectional Gaussian
relay network to within 3 bits/sec/Hz per user is characterized.Comment: IEEE Trans. on Information Theory, accepte
Using Network Coding to Achieve the Capacity of Deterministic Relay Networks with Relay Messages
In this paper, we derive the capacity of the deterministic relay networks
with relay messages. We consider a network which consists of five nodes, four
of which can only communicate via the fifth one. However, the fifth node is not
merely a relay as it may exchange private messages with the other network
nodes. First, we develop an upper bound on the capacity region based on the
notion of a single sided genie. In the course of the achievability proof, we
also derive the deterministic capacity of a 4-user relay network (without
private messages at the relay). The capacity achieving schemes use a
combination of two network coding techniques: the Simple Ordering Scheme (SOS)
and Detour Schemes (DS). In the SOS, we order the transmitted bits at each user
such that the bi-directional messages will be received at the same channel
level at the relay, while the basic idea behind the DS is that some parts of
the message follow an indirect path to their respective destinations. This
paper, therefore, serves to show that user cooperation and network coding can
enhance throughput, even when the users are not directly connected to each
other.Comment: 12 pages, 5 figures, submitted to IEEE JSAC Network codin
The Deterministic Capacity of Relay Networks with Relay Private Messages
We study the capacity region of a deterministic 4-node network, where 3 nodes
can only communicate via the fourth one. However, the fourth node is not merely
a relay since it can exchange private messages with all other nodes. This
situation resembles the case where a base station relays messages between users
and delivers messages between the backbone system and the users. We assume an
asymmetric scenario where the channel between any two nodes is not reciprocal.
First, an upper bound on the capacity region is obtained based on the notion of
single sided genie. Subsequently, we construct an achievable scheme that
achieves this upper bound using a superposition of broadcasting node 4 messages
and an achievable "detour" scheme for a reduced 3-user relay network.Comment: 3 figures, accepted at ITW 201
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
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]
On Achievable Rate Regions of the Asymmetric AWGN Two-Way Relay Channel
This paper investigates the additive white Gaussian noise two-way relay
channel, where two users exchange messages through a relay. Asymmetrical
channels are considered where the users can transmit data at different rates
and at different power levels. We modify and improve existing coding schemes to
obtain three new achievable rate regions. Comparing four downlink-optimal
coding schemes, we show that the scheme that gives the best sum-rate
performance is (i) complete-decode-forward, when both users transmit at low
signal-to-noise ratio (SNR); (ii) functional-decode-forward with nested lattice
codes, when both users transmit at high SNR; (iii) functional-decode-forward
with rate splitting and time-division multiplexing, when one user transmits at
low SNR and another user at medium--high SNR.Comment: to be presented at ISIT 201
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