Codex Corporation

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

Finite word-length effects in recursive least squares algorithms with application to adaptive equalization

Abstract: In this paper we provide a summary of recent and new results on finite word length effects in recursive least squares adaptive algorithms. We define the numerical accuracy and numerical stability of adaptive recursive least squares algorithms and show that these two properties are related to each other, but are not equivalent. The numerical stability of adaptive recursive least squares algorithms is analyzed theoretically and the numerical accuracy with finite word length is investigated by computer simulation. It is shown that the conventional recursive least squares algorithm gives poor numerical accuracy when a short word length is used. A new form of a recursive least squares lattice algorithm is presented which is more robust to round-off errors compared to the conventional form. Optimum scaling of recursive least squares algorithms for fixedpoint implementation is also considered.

Convergence characteristics of LMS and LS adaptive algorithms for signals with rank-deficient correlation matrices

Abstract: The author investigates the convergence characteristics of the last mean square (LMS) and the recursive least squares (RLS) adaptive algorithms when the correlation matrix of the input signal does not have a full rank. It is shown that the initial convergence rate of the LMS algorithm is inversely proportional to the rank of correlation matrix, or equivalently, the number of nonzero eigenvalues. The same conclusion holds for the RLS algorithms if the minimum norm solution (MNS) is used in each iteration. A simple time-recursive method to obtain approximate MNSs in each iteration is presented and proven. The effect of additive noise is discussed. >

Correlation-based fast training of data-driven Nyquist in-band echo cancellers

Abstract: A novel echo canceller fast training scheme for data-driven 'Nyquist' in-band echo cancellers is presented. This scheme simultaneously estimates the near and far echo canceller coefficients by sending a special periodic training sequence and correlating a segment of the sequence with the real echo samples of the sequence. The requirements and the generation of such a training sequence are discussed and described in detail. Fast initialization of a phase-roll compensator is also discussed. The proposed scheme is compared with other echo canceller training schemes. >

Dual tone multi-frequency detector

Abstract: An apparatus for identifying a first tone and a second tone present in a dual-tone signal, the first tone being selected from a group of tones located within a low band and the second tone being selected from a second group of tones located within a high band, the low band and the high band each spanning a frequency range no greater than f0 wide, the apparatus including a first filter for isolating and downconverting the portion of the dual-tone signal falling within the low band so that it lies within a low frequency range extending from -f0 to F0 ; and a second filter for isolating and downconverting the portion of the dual-tone signal falling within the high band so that it lies within the low frequency range.

Programmable frequency divider in a phase lock loop

Abstract: A phase lock loop (10) monitors a first digital signal and generates a second digital signal operating substantially at frequency and in-phase with the first digital signal A programmable divider (30) latches (60) a program integer for providing a latch integer, compares (64) the latch integer to a constant integer, and generates a flag signal having a first state when the latch integer mismatches the constant integer and a second state when the latch integer matches the constant integer The latch integer is decremented (62) when the flag signal has the first state The flag signal is delayed in response to first and second clock signals for providing the second digital signal having a frequency determined by the program integer The first and second digital signals are applied to a lock detection circuit for providing a lock detection signal