248 research outputs found
Reconfigurable rateless codes
We propose novel reconfigurable rateless codes, that are capable of not only varying the block length but also adaptively modify their encoding strategy by incrementally adjusting their degree distribution according to the prevalent channel conditions without the availability of the channel state information at the transmitter. In particular, we characterize a reconfigurable ratelesscode designed for the transmission of 9,500 information bits that achieves a performance, which is approximately 1 dB away from the discrete-input continuous-output memoryless channel’s (DCMC) capacity over a diverse range of channel signal-to-noise (SNR) ratios
Reconfigurable rateless codes
We propose novel reconfigurable rateless codes, that are capable of not only varying the block length but also adaptively modify their encoding strategy by incrementally adjusting their degree distribution according to the prevalent channel conditions without the availability of the channel state information at the transmitter. In particular, we characterize a reconfigurable ratelesscode designed for the transmission of 9,500 information bits that achieves a performance, which is approximately 1 dB away from the discrete-input continuous-output memoryless channel’s (DCMC) capacity over a diverse range of channel signal-to-noise (SNR) ratios
Using Channel Output Feedback to Increase Throughput in Hybrid-ARQ
Hybrid-ARQ protocols have become common in many packet transmission systems
due to their incorporation in various standards. Hybrid-ARQ combines the normal
automatic repeat request (ARQ) method with error correction codes to increase
reliability and throughput. In this paper, we look at improving upon this
performance using feedback information from the receiver, in particular, using
a powerful forward error correction (FEC) code in conjunction with a proposed
linear feedback code for the Rayleigh block fading channels. The new hybrid-ARQ
scheme is initially developed for full received packet feedback in a
point-to-point link. It is then extended to various different multiple-antenna
scenarios (MISO/MIMO) with varying amounts of packet feedback information.
Simulations illustrate gains in throughput.Comment: 30 page
Optimizing HARQ and relay strategies in limited feedback communication systems
One of the key challenges for future communication systems is to deal with fast changing channels due to the mobility of users. Having a robust protocol capable of handling transmission failures in unfavorable channel conditions is crucial, but the feedback capacity may be greatly limited due to strict latency requirements. This paper studies the hybrid automatic repeat request (HARQ) techniques involved in re-transmissions when decoding failures occur at the receiver and proposes a scheme that relies on codeword bundling and adaptive incremental redundancy (IR) to maximize the overall throughput in a limited feedback system. In addition to the traditional codeword extension IR bits, this paper introduces a new type of IR, bundle parity bits, obtained from an erasure code across all the codewords in a bundle. The type and number of IR bits to be sent as a response to a decoding failure is optimized through a Markov Decision Process. In addition to the single link analysis, the paper studies how the same techniques generalize to relay and multi-user broadcast systems. Simulation results show that the proposed schemes can provide a significant increase in throughput over traditional HARQ techniques
A Systematic Approach to Incremental Redundancy over Erasure Channels
As sensing and instrumentation play an increasingly important role in systems
controlled over wired and wireless networks, the need to better understand
delay-sensitive communication becomes a prime issue. Along these lines, this
article studies the operation of data links that employ incremental redundancy
as a practical means to protect information from the effects of unreliable
channels. Specifically, this work extends a powerful methodology termed
sequential differential optimization to choose near-optimal block sizes for
hybrid ARQ over erasure channels. In doing so, an interesting connection
between random coding and well-known constants in number theory is established.
Furthermore, results show that the impact of the coding strategy adopted and
the propensity of the channel to erase symbols naturally decouple when
analyzing throughput. Overall, block size selection is motivated by normal
approximations on the probability of decoding success at every stage of the
incremental transmission process. This novel perspective, which rigorously
bridges hybrid ARQ and coding, offers a pragmatic means to select code rates
and blocklengths for incremental redundancy.Comment: 7 pages, 2 figures; A shorter version of this article will appear in
the proceedings of ISIT 201
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