1,335 research outputs found
Multilevel Coding Schemes for Compute-and-Forward with Flexible Decoding
We consider the design of coding schemes for the wireless two-way relaying
channel when there is no channel state information at the transmitter. In the
spirit of the compute and forward paradigm, we present a multilevel coding
scheme that permits computation (or, decoding) of a class of functions at the
relay. The function to be computed (or, decoded) is then chosen depending on
the channel realization. We define such a class of functions which can be
decoded at the relay using the proposed coding scheme and derive rates that are
universally achievable over a set of channel gains when this class of functions
is used at the relay. We develop our framework with general modulation formats
in mind, but numerical results are presented for the case where each node
transmits using the QPSK constellation. Numerical results with QPSK show that
the flexibility afforded by our proposed scheme results in substantially higher
rates than those achievable by always using a fixed function or by adapting the
function at the relay but coding over GF(4).Comment: This paper was submitted to IEEE Transactions on Information Theory
in July 2011. A shorter version also appeared in the proceedings of the
International Symposium on Information Theory in August 2011 without the
proof of the main theore
A Quantum Multiparty Packing Lemma and the Relay Channel
Optimally encoding classical information in a quantum system is one of the
oldest and most fundamental challenges of quantum information theory. Holevo's
bound places a hard upper limit on such encodings, while the
Holevo-Schumacher-Westmoreland (HSW) theorem addresses the question of how many
classical messages can be "packed" into a given quantum system. In this
article, we use Sen's recent quantum joint typicality results to prove a
one-shot multiparty quantum packing lemma generalizing the HSW theorem. The
lemma is designed to be easily applicable in many network communication
scenarios. As an illustration, we use it to straightforwardly obtain quantum
generalizations of well-known classical coding schemes for the relay channel:
multihop, coherent multihop, decode-forward, and partial decode-forward. We
provide both finite blocklength and asymptotic results, the latter matching
existing classical formulas. Given the key role of the classical packing lemma
in network information theory, our packing lemma should help open the field to
direct quantum generalization.Comment: 20 page
Some Empirical Criteria for Attributing Creativity to a Computer Program
Peer reviewedPostprin
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
- ā¦