1,718 research outputs found
On the Capacity Region of the Two-user Interference Channel with a Cognitive Relay
This paper considers a variation of the classical two-user interference
channel where the communication of two interfering source-destination pairs is
aided by an additional node that has a priori knowledge of the messages to be
transmitted, which is referred to as the it cognitive relay. For this
Interference Channel with a Cognitive Relay (ICCR) In particular, for the class
of injective semi-deterministic ICCRs, a sum-rate upper bound is derived for
the general memoryless ICCR and further tightened for the Linear Deterministic
Approximation (LDA) of the Gaussian noise channel at high SNR, which disregards
the noise and focuses on the interaction among the users' signals. The capacity
region of the symmetric LDA is completely characterized except for the regime
of moderately weak interference and weak links from the CR to the destinations.
The insights gained from the analysis of the LDA are then translated back to
the symmetric Gaussian noise channel (GICCR). For the symmetric GICCR, an
approximate characterization (to within a constant gap) of the capacity region
is provided for a parameter regime where capacity was previously unknown. The
approximately optimal scheme suggests that message cognition at a relay is
beneficial for interference management as it enables simultaneous over the air
neutralization of the interference at both destinations
On the Capacity of the Two-user Gaussian Causal Cognitive Interference Channel
This paper considers the two-user Gaussian Causal Cognitive Interference
Channel (GCCIC), which consists of two source-destination pairs that share the
same channel and where one full-duplex cognitive source can causally learn the
message of the primary source through a noisy link. The GCCIC is an
interference channel with unilateral source cooperation that better models
practical cognitive radio networks than the commonly used model which assumes
that one source has perfect non-causal knowledge of the other source's message.
First the sum-capacity of the symmetric GCCIC is determined to within a
constant gap. Then, the insights gained from the derivation of the symmetric
sum-capacity are extended to characterize the whole capacity region to within a
constant gap for more general cases. In particular, the capacity is determined
(a) to within 2 bits for the fully connected GCCIC when, roughly speaking, the
interference is not weak at both receivers, (b) to within 2 bits for the
Z-channel, i.e., when there is no interference from the primary user, and (c)
to within 2 bits for the S-channel, i.e., when there is no interference from
the secondary user. The parameter regimes where the GCCIC is equivalent, in
terms of generalized degrees-of-freedom, to the noncooperative interference
channel (i.e., unilateral causal cooperation is not useful), to the non-causal
cognitive interference channel (i.e., causal cooperation attains the ultimate
limit of cognitive radio technology), and to bilateral source cooperation are
identified. These comparisons shed lights into the parameter regimes and
network topologies that in practice might provide an unbounded throughput gain
compared to currently available (non cognitive) technologies.Comment: Under second round review in IEEE Transactions in Information Theory
- Submitted September 201
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