12,817 research outputs found
Cooperative Relay Broadcast Channels
The capacity regions are investigated for two relay broadcast channels
(RBCs), where relay links are incorporated into standard two-user broadcast
channels to support user cooperation. In the first channel, the Partially
Cooperative Relay Broadcast Channel, only one user in the system can act as a
relay and transmit to the other user through a relay link. An achievable rate
region is derived based on the relay using the decode-and-forward scheme. An
outer bound on the capacity region is derived and is shown to be tighter than
the cut-set bound. For the special case where the Partially Cooperative RBC is
degraded, the achievable rate region is shown to be tight and provides the
capacity region. Gaussian Partially Cooperative RBCs and Partially Cooperative
RBCs with feedback are further studied. In the second channel model being
studied in the paper, the Fully Cooperative Relay Broadcast Channel, both users
can act as relay nodes and transmit to each other through relay links. This is
a more general model than the Partially Cooperative RBC. All the results for
Partially Cooperative RBCs are correspondingly generalized to the Fully
Cooperative RBCs. It is further shown that the AWGN Fully Cooperative RBC has a
larger achievable rate region than the AWGN Partially Cooperative RBC. The
results illustrate that relaying and user cooperation are powerful techniques
in improving the capacity of broadcast channels.Comment: Submitted to the IEEE Transactions on Information Theory, July 200
Cooperative Strategies for Simultaneous and Broadcast Relay Channels
Consider the \emph{simultaneous relay channel} (SRC) which consists of a set
of relay channels where the source wishes to transmit common and private
information to each of the destinations. This problem is recognized as being
equivalent to that of sending common and private information to several
destinations in presence of helper relays where each channel outcome becomes a
branch of the \emph{broadcast relay channel} (BRC). Cooperative schemes and
capacity region for a set with two memoryless relay channels are investigated.
The proposed coding schemes, based on \emph{Decode-and-Forward} (DF) and
\emph{Compress-and-Forward} (CF) must be capable of transmitting information
simultaneously to all destinations in such set.
Depending on the quality of source-to-relay and relay-to-destination
channels, inner bounds on the capacity of the general BRC are derived. Three
cases of particular interest are considered: cooperation is based on DF
strategy for both users --referred to as DF-DF region--, cooperation is based
on CF strategy for both users --referred to as CF-CF region--, and cooperation
is based on DF strategy for one destination and CF for the other --referred to
as DF-CF region--. These results can be seen as a generalization and hence
unification of previous works. An outer-bound on the capacity of the general
BRC is also derived. Capacity results are obtained for the specific cases of
semi-degraded and degraded Gaussian simultaneous relay channels. Rates are
evaluated for Gaussian models where the source must guarantee a minimum amount
of information to both users while additional information is sent to each of
them.Comment: 32 pages, 7 figures, To appear in IEEE Trans. on Information Theor
Rate Regions for the Partially-Cooperative Relay Broadcast Channel with Non-causal Side Information
In this work, we consider a partially cooperative relay broadcast channel
(PC-RBC) controlled by random parameters. We provide rate regions for two
different situations: 1) when side information (SI) S^n on the random
parameters is non-causally known at both the source and the relay and, 2) when
side information S^n is non-causally known at the source only. These achievable
regions are derived for the general discrete memoryless case first and then
extended to the case when the channel is degraded Gaussian and the SI is
additive i.i.d. Gaussian. In this case, the source uses generalized dirty paper
coding (GDPC), i.e., DPC combined with partial state cancellation, when only
the source is informed, and DPC alone when both the source and the relay are
informed. It appears that, even though it can not completely eliminate the
effect of the SI (in contrast to the case of source and relay being informed),
GDPC is particularly useful when only the source is informed.Comment: 7 pages, Proc. of IEEE International Symposium on Information theory,
ISIT 2007, Nice, Franc
Broadcast Capacity Region of Two-Phase Bidirectional Relaying
In a three-node network a half-duplex relay node enables bidirectional
communication between two nodes with a spectral efficient two phase protocol.
In the first phase, two nodes transmit their message to the relay node, which
decodes the messages and broadcast a re-encoded composition in the second
phase. In this work we determine the capacity region of the broadcast phase. In
this scenario each receiving node has perfect information about the message
that is intended for the other node. The resulting set of achievable rates of
the two-phase bidirectional relaying includes the region which can be achieved
by applying XOR on the decoded messages at the relay node. We also prove the
strong converse for the maximum error probability and show that this implies
that the [\eps_1,\eps_2]-capacity region defined with respect to the average
error probability is constant for small values of error parameters \eps_1,
\eps_2.Comment: 25 pages, 2 figures, submitted to IEEE Transactions on Information
Theor
Achievable Rate Regions of Two-Way Relay Channels
With the fast development of communication networks, cooperative communication has been more widely used in many different fields, such as satellite networks, broadcast networks, internet and so on. Therefore relay channels have been playing a pivotal role since their definitions were proposed by Van-der Meulen. However, the general achievable rate region of a relay channel is still unknown which inspires more people to persistently work on. There are several different kinds of coding schemes proposed by people after relay channels came into our lives. Until now, the two most commonly used coding strategies of relay channels are Decode-and-Forward and Compress-and-Forward. In this thesis we will provide a way to obtain the achievable rate region for two-way relay channels by using decode-and-forward coding.
With the knowledge of basic information theory and network information theory, we will focus our study on the achievable rates of relay channels. Most of the previous study of relay channels are aiming to find a more general achievable rate region. In this thesis, an intuitional way will be used to study four-terminal relay channels. This method makes a good use of the information from three-terminal relay channels by separating a four-terminal relay channel into two parts: (1). a three-terminal relay channel; (2). a common end node. The final achievable rate region is obtained by combing together the separate achievable rates of the two parts. We split the complex model to two easier ones, this idea may give help for doing researches on more complicated channels.
Eliminating interferences is also a difficulty in the study of relay channels. Comparing with the achievable rate regions of two-way two-relay channels which have already been proved, we found that it is feasible to separate a two-way two-relay channel into a three-terminal relay channel and an common end node. Therefore, we apply this method to all two-way four-terminal relay channels. After fixing two different source nodes, all of the possible transmission schemes are presented in this thesis. However not all of the four-terminal channels can be separated into two parts. By studying the schemes failed to be decomposed to a three-terminal relay channel and a common end node, we found that these schemes are infeasible for message transmission. Thus our method can still be used to study on feasible two-way relay channels
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