123 research outputs found
Precoding for coded communication on block fading channels and cooperative communications
We study precoding for the outage probability minimization of block fading (BF) channels and BF relay channels. Recently, an upper bound on the outage probability with precoding was established for BF channels, but only for high instantaneous SNR. This upper bound is much easier to minimize than the actual outage probability, so that optimal precoding matrices can be determined without much computational effort. Here, we provide a proof for the upper bound on the outage probability at low instantaneous SNR. Next, the structure of the precoding matrix is simplified so that it can be easily constructed for an arbitrary number of blocks in the BF channel. Finally, we apply this technique to cooperative communications
The Role of Cryptography in Our Information-Based Society
Presentation given virtually at TAMUQ on 2 July 202
Irregular Turbo Codes in Block-Fading Channels
We study irregular binary turbo codes over non-ergodic block-fading channels.
We first propose an extension of channel multiplexers initially designed for
regular turbo codes. We then show that, using these multiplexers, irregular
turbo codes that exhibit a small decoding threshold over the ergodic
Gaussian-noise channel perform very close to the outage probability on
block-fading channels, from both density evolution and finite-length
perspectives.Comment: to be presented at the IEEE International Symposium on Information
Theory, 201
Low-Density Graph Codes for slow fading Relay Channels
We study Low-Density Parity-Check (LDPC) codes with iterative decoding on
block-fading (BF) Relay Channels. We consider two users that employ coded
cooperation, a variant of decode-and-forward with a smaller outage probability
than the latter. An outage probability analysis for discrete constellations
shows that full diversity can be achieved only when the coding rate does not
exceed a maximum value that depends on the level of cooperation. We derive a
new code structure by extending the previously published full-diversity
root-LDPC code, designed for the BF point-to-point channel, to exhibit a
rate-compatibility property which is necessary for coded cooperation. We
estimate the asymptotic performance through a new density evolution analysis
and the word error rate performance is determined for finite length codes. We
show that our code construction exhibits near-outage limit performance for all
block lengths and for a range of coding rates up to 0.5, which is the highest
possible coding rate for two cooperating users.Comment: Accepted for publication in IEEE Transactions on Information Theor
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