52 research outputs found
Asymmetric Compute-and-Forward with CSIT
We present a modified compute-and-forward scheme which utilizes Channel State
Information at the Transmitters (CSIT) in a natural way. The modified scheme
allows different users to have different coding rates, and use CSIT to achieve
larger rate region. This idea is applicable to all systems which use the
compute-and-forward technique and can be arbitrarily better than the regular
scheme in some settings.Comment: in International Zurich Seminar on Communications, 2014; minor update
on example
Lattice Codes for Many-to-One Interference Channels With and Without Cognitive Messages
A new achievable rate region is given for the Gaussian cognitive many-to-one
interference channel. The proposed novel coding scheme is based on the
compute-and-forward approach with lattice codes. Using the idea of decoding
sums of codewords, our scheme improves considerably upon the conventional
coding schemes which treat interference as noise or decode messages
simultaneously. Our strategy also extends directly to the usual many-to-one
interference channels without cognitive messages. Comparing to the usual
compute-and-forward scheme where a fixed lattice is used for the code
construction, the novel scheme employs scaled lattices and also encompasses key
ingredients of the existing schemes for the cognitive interference channel.
With this new component, our scheme achieves a larger rate region in general.
For some symmetric channel settings, new constant gap or capacity results are
established, which are independent of the number of users in the system.Comment: To appear in IEEE Transactions on Information Theor
Gaussian Multiple Access via Compute-and-Forward
Lattice codes used under the Compute-and-Forward paradigm suggest an
alternative strategy for the standard Gaussian multiple-access channel (MAC):
The receiver successively decodes integer linear combinations of the messages
until it can invert and recover all messages. In this paper, a multiple-access
technique called CFMA (Compute-Forward Multiple Access) is proposed and
analyzed. For the two-user MAC, it is shown that without time-sharing, the
entire capacity region can be attained using CFMA with a single-user decoder as
soon as the signal-to-noise ratios are above . A partial analysis
is given for more than two users. Lastly the strategy is extended to the
so-called dirty MAC where two interfering signals are known non-causally to the
two transmitters in a distributed fashion. Our scheme extends the previously
known results and gives new achievable rate regions.Comment: to appear in IEEE Transactions on Information Theor
Semi-Supervised Learning: the Case When Unlabeled Data is Equally Useful
Semi-supervised learning algorithms attempt to take advantage of relatively
inexpensive unlabeled data to improve learning performance. In this work, we
consider statistical models where the data distributions can be characterized
by continuous parameters. We show that under certain conditions on the
distribution, unlabeled data is equally useful as labeled date in terms of
learning rate. Specifically, let be the number of labeled and unlabeled
data, respectively. It is shown that the learning rate of semi-supervised
learning scales as if , and scales as if
for some , whereas the learning rate of
supervised learning scales as .Comment: accepted to UAI 202
Cooperative Secret Communication with Artificial Noise in Symmetric Interference Channel
We consider the symmetric Gaussian interference channel where two users try
to enhance their secrecy rates in a cooperative manner. Artificial noise is
introduced along with useful information. We derive the power control and
artificial noise parameter for two kinds of optimal points, max-min point and
single user point. It is shown that there exists a critical value of the
power constraint, below which the max-min point is an optimal point on the
secrecy rate region, and above which time-sharing between single user points
achieves larger secrecy rate pairs. It is also shown that artificial noise can
help to enlarge the secrecy rate region, in particular on the single user
point.Comment: 3 pages, 3 figures, to appear in IEEE Communications Letter
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