1229 compression of files of information retrieval systems. With this application in mind, bounds on the average codelength of an alphabetical code were studied. The major results of this correspondence are as follows. 1) A necessary and sufficient condition for the existence of a 2) An upper bound for Lopt (the average codelength of the binary alphabetical code was given. optimal alphabetical ...

An (n,M, d; q) code is called equidistant code if the Hamming distance between any two codewords is d. It was proved that for any equidistant (n,M, d; q) code, d nM(q − 1)/(M − 1)q(= dopt, say). A necessary condition for the existence of an optimal equidistant code is that dopt be an integer. If dopt is not an integer, i.e. the equidistant code is not optimal, then the code with d = dopt is cal...

An A-code is an extension of A-code in which none of the three participants, transmitter, receiver and arbiter, is assumed trusted. In this paper we extend the previous model of A-codes by allowing transmitter and receiver not only to individually attack the system but also collude with the arbiter against the other. We derive informationtheoretic lower bounds on success probability of various ...

A (v, k, λ) optical orthogonal code C is a family of (0, 1) sequences of length v and weight k satisfying the following two correlation properties: (1) ∑ 0≤t≤v−1xtxt+i ≤ λ for any x = (x0, x1, . . . , xv−1) ∈ C and any integer i 6≡ 0 (mod v); (2) ∑ 0≤t≤v−1xtyt+i ≤ λ for any x = (x0, x1, . . . , xv−1) ∈ C, y = (y0,y1, . . ., yv−1) ∈ C with x 6= y, and any integer i, where the subscripts are take...

This report provides an overview of major results we have obtained in the research project “Constructions of Diversity-Multiplexing Tradeoff Optimal Codes for Multiuser MIMO Systems with Applications to MIMO Mobile Communications” supported by National Science Council under contract number NSC98 2221 E 009 045 MY3 during August 2009 July 2012. In this report, we are concentrating explicit code ...