arXiv subjects

Tamás Kói

Publications and source records attributed to Tamás Kói.

4 recordsLinked to original sources

arXiv2020

Error Exponents for Asynchronous Multiple Access Channels. Controlled Asynchronism may Outperform Synchronism

Exponential error bounds achievable by universal coding and decoding are derived for frame-asynchronous discrete memoryless %asynchronous multiple access channels with two senders, via the method of subtypes, a refinement of the method of types. Maximum empirical multi-information decoding is employed. A key tool is an improved packing lemma, that overcomes the technical difficulty caused by codeword repetitions, via an induction based new argument. The asymptotic form of the bounds admits numerical evaluation. This demostrates that error exponents achievable by synchronous transmission (if possible) can be superseeded via controlled asynchronism, i.e. a deliberate shift of the codewords.

cs.IT↗

arXiv2017

Universal Random Access Error Exponents for Codebooks of Different Word-Lengths

Csiszár's channel coding theorem for multiple codebooks is generalized allowing the codeword lenghts differ across codebooks. Also in this case, for each codebook an error exponent can be achieved that equals the random coding exponent for this codebook alone, in addition, erasure detection failure probability tends to 0. This is proved even for sender and receiver not knowing the channel. As a corollary, a substantial improvement is obtained when the sender knows the channel.

cs.IT↗

arXiv2014

On Capacity Regions of Discrete Asynchronous Multiple Access Channels

A general formalization is given for asynchronous multiple access channels which admits different assumptions on delays. This general framework allows the analysis of so far unexplored models leading to new interesting capacity regions. In particular, a single letter characterization is given for the capacity region in case of 3 senders, 2 synchronous with each other and the third not synchronous with them.

cs.IT↗

arXiv2013

Random Access and Source-Channel Coding Error Exponents for Multiple Access Channels

A new universal coding/decoding scheme for random access with collision detection is given in the case of two senders. The result is used to give an achievable joint source-channel coding error exponent for multiple access channels in the case of independent sources. This exponent is improved in a modified model that admits error free 0 rate communication between the senders.

cs.IT↗