A table of binary constant weight codes of length nl28 is presented. Explicit constructions are given for most of the 600 codes in the table; the majority of these codes are new. The known techniques for constructing constant weight codes are surveyed, and a table of (unrestricted) binary codes of length nl28 is given

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A new table of constant weight codes

An optical orthogonal signature pattern code (OOSPC) is a collection of (0,1) two-dimensional (2-D) patterns with good correlation properties (i.e., high autocorrelation peaks with low sidelobes, and low cross-correlation functions). Such codes find applications, for example, to parallelly transmit and access images in "multicore-fiber" code-division multiple-access (CDMA) networks. Up to now all work on OOSPCs has been based on an assumption that at most one pulse per column or one pulse per row and column is allowed in each two-dimensional pattern. However, this restriction may not be required in such multiple-access networks if timing information can be extracted from other means, rather than from the autocorrelation function. A new class of OOSPCs is constructed without the restriction. The relationships between two-dimensional binary discrete auto- and cross-correlation arrays and their corresponding "sets" for OOSPCs are first developed. In addition, new bounds on the size of this special class of OOSPCs are derived. Afterwards, four algebraic techniques for constructing these new codes are investigated. Among these constructions, some of them achieve the upper bounds with equality and are thus optimal. Finally, the codes generated from some constructions satisfy the restriction of at most one pulse per row or column and hence can be used in applications requiring, for example, frequency-hopping patterns.

Two-dimensional spatial signature patterns

To simultaneously support multimedia services with different signaling rates and quality-of-service requirements in optical code division multiple access (CDMA) networks, a new class of multilength, constant-weight optical orthogonal codes (OOCs) with good correlation properties is constructed algebraically in this paper. The performance of these new OOCs in an optical CDMA system with double-media services is analyzed. In contrast to conventional CDMA, our study shows that the performance of these multilength OOCs worsens as the code length increases, allowing prioritization in optical CDMA. Finally, an application of these multilength OOCs to integrate different types of multimedia services is briefly discussed.

Design of multilength optical orthogonal codes for optical CDMA multimedia networks

We present a new recursive construction for (n,/spl omega/,/spl lambda//sub a/,/spl lambda//sub c/) optical orthogonal codes. For the case of /spl lambda//sub a/ = /spl lambda//sub c/ = /spl lambda/, this recursive construction enlarges the original family with /spl lambda/ unchanged, and produces a new family of asymptotically optimal codes, if the original family is asymptotically optimal. We call a code asymptotically optimal, following the definition of O. Moreno et al. (see ibid., vol.41, p.448-55, 1995), if, as n, the length of code, goes to infinity, the ratio of the number of codewords to the corresponding Johnson bound approaches unity.

A new recursive construction for optical orthogonal codes

The goals of this article are twofold: (1) to provide a brief tutorial of the application of low-density parity check (LDPC) codes for partial response (PR) channels under the framework of turbo equalization and (2) to highlight the use of structured LDPC codes in PR systems. We begin by introducing LDPC codes, their graph representations and associated sum-product decoding algorithm, followed by describing the general framework of iterative equalization and decoding approach to combat ISI. We then present explicit constructions of structured LDPC codes, which facilitate efficient implementation of encoding and decoding and show simulation results.

Low-density parity check codes for partial response channels

A lower bound on the length of binary self-orthogonal unequal error protection (UEP) codes is derived, and two design procedures for constructing optimal self-orthogonal UEP codes are proposed. With this lower bound, known self-orthogonal UEP codes can be evaluated. It is pointed out that, for given values of minimum distance and code rate, the self-orthogonal codes must be relatively long, so optimal self-orthogonal codes are not optimal in general. But self-orthogonal codes can be implemented simply, and they have error-correcting capabilities beyond those guaranteed by their minimum distance. These properties can be viewed as a partial compensation for using self-orthogonal codes. >

New results on self-orthogonal unequal error protection codes

New classes of multi-level and complex sequences with perfect periodic autocorrelations are presented. The sequences are derived directly from certain M-sequences over rational and Gaussian integers.

Perfect sequences derived from M-sequences

A new binary (22,13,5) quasi-perfect code is presented. The weight distributions of the coset codes are given. The code obtained is not equivalent to T.J. Wagner's code (1966). Four lower bounds for constant weight codes can be derived from it, which are better than the codes with the same parameters in R.L. Graham and N.J. Sloane (1980) and A.E. Brouwer et al. (1980). >

On a new binary (22,13,5) code

Disjoint difference sets (DDS), difference triangle sets (DTS), and related codes are discussed and a recursive construction for DDS is given With this construction and the relationship between DDS and DTS, many new upper bounds for DTS and some better orthogonal codes are obtained >

Disjoint difference sets, difference triangle sets, and related codes

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New results on self-orthogonal unequal error protection codes

Perfect sequences derived from M-sequences

On a new binary (22,13,5) code

Disjoint difference sets, difference triangle sets, and related codes