Codex Corporation

About: Codex Corporation is a based out in . It is known for research contribution in the topics: Signal & Network packet. The organization has 189 authors who have published 241 publications receiving 32205 citations.

Coset codes. I. Introduction and geometrical classification

Abstract: Practically all known good constructive coding techniques for bandlimited channels, including lattice codes and various trellis-coded modulation schemes, can be characterized as coset codes. A coset code is defined by a lattice partition Lambda / Lambda ' and by a binary encoder C that selects a sequence of cosets of the lattice Lambda '. The fundamental coding gain of a coset code, as well as other important parameters such as the error coefficient, the decoding complexity, and the constellation expansion factor, are purely geometric parameters determined by C Lambda / Lambda '. The known types of coset codes, as well as a number of new classes that systematize and generalize known codes, are classified and compared in terms of these parameters. >

Multidimensional constellations. I. Introduction, figures of merit, and generalized cross constellations

Abstract: The authors discuss the major attributes desired in signal constellations, such as signal-to-noise ratio (SNR) efficiency, simplicity of mapping bits to points and vice versa, compatibility with coded modulation schemes, and compatibility with quadrature amplitude modulation (QAM). The capability of supporting a so-called opportunistic secondary channel, often used for internal control signaling, is considered. The gain in SNR efficiency of a multidimensional constellation (lattice code) consisting of the points from a lattice Lambda within a region R compared to a cubic constellation is shown to be approximately separable into the coding gain of Lambda and the shape gain of R, for large constellations. Similarly, the expansion of the associated constituent 2-D constellation is shown to be approximately separable into a constellation expansion ratio (CER) coding component CER/sub c/( Lambda ) and a shaping component CER/sub s/(R). The N sphere is the region R with the best shape gain, but N also has large constellation expansion. Bounds for the best possible shape gain versus CER/sub s/(R) or peak-to-average-power ratio (PAR) are given. Generalized cross constellations are discussed. These constellations yield a modest shape gain with very low CER/sub s/(R) or PAR, are easily implemented, are well suited for use with coded QAM modems, and can be readily adapted to support an opportunistic secondary channel. >

The OSI reference model

Abstract: The early successes of computer networks in the mid-1970's made it apparent that to utilize the full potential of computer networks, international standards would be required. In 1977, the International Standards Organization (ISO) initiated work on Open Systems Interconnection (OSI) to address these requirements. This paper briefly describes the OSI Reference Model. The OSI Reference Model is the highest level of abstraction in the OSI scheme. The paper first describes the basic building blocks used to construct the network model. Then the particular seven-layer model used by OSI is briefly described, followed by a discussion of outstanding issues and future extensions for the model.

The LMS algorithm with delayed coefficient adaptation

Abstract: The behavior of the delayed least-mean-square (DLMS) algorithm is studied. It is found that the step size in the coefficient update plays a key role in the convergence and stability of the algorithm. An upper bound for the step size is derived that ensures the stability of the DLMS. The relationship between the step size and the convergence speed, and the effect of the delay on the convergence speed, are also studied. The analytical results are supported by computer simulations. >

Method for prioritizing, selectively discarding, and multiplexing differing traffic type fast packets

Abstract: A queueing and dequeueing mechanism for use in an integrated fast packet network, wherein fast packets from differing traffic types are multiplexed with one another through use of a weighted round-robin bandwidth allocation mechanism (517). Fast packets within a particular traffic type are selected for transmission through use of a head of line priority service (514), a packet discard mechanism (516), or both. The weighted round-robin bandwidth allocation mechanism functions, in part, based upon a credit counter for each queue group that represents a particular traffic type.